In fact, since I wrote the below, the online terrain has changed signicantly. There are now great tools available, particularly:
Any serious student of Japanese will want to learn two or three thousand kanji ("chinese characters"). Fortunately this is an interesting, challenging, and pleasant task, especially with the proper learning aids. I recommend three main tools: good kanji dictionaries by Halpern and Nelson, the books and flashcards by Heisig, and the portable electronic Wordtank dictionaries made by Canon.
This is a reprint of the dictionary originally produced by Kenkyusha in the early 1990's. Its SKIP system of kanji lookup is far faster than the traditional radical system for characters whose readings are unknown to the reader. It has lots of useful lists of kanji synonomys, historical tables, and other invaluable cultural information for the beginner. Its biggest weakness is that it only has 3587 entries, a number of which are just variant forms. This is fine for the beginning and intermediate student of Japanese, but too few for the advanced student.
This is a shorter version of the above. Same strengths and weakness as above, but more portable. I'll probably get on just to see what it looks like. (I only realized that it existed last weekend...)
Nelson was the standard character dictionary for English speakers for decades after it was published. It has much better coverage (7000ish entries) than Halpern, and uses a somewhat simplified system of radical lookup over the convoluted traditional radical system. Any serious student of Japanese will want to have both.
There are also kanjijiten by Hademitzky and Spahn. The main virtue of the latter is that one can look up a compound by any character within it, not just the first. This is especially useful for kanji that (almost) only appear in second or third position. I've never owned one, except for there very brief listing of the jouyou kanji, whose advice on learning kanji was pedestrian.
As far as learning kanji goes, you can't do better than the wonderful books by James W. Heisig.
These are all published by the Japan Publications Trading Company. There is a beautiful set of 2042 flashcards that go with volumes I and II, which I also highly recommend.
According to one satisfied Amazon customer (Sean McLennan
The system that James Heisig presents in the "Remembering the Kanji" series is the fastest and most effective way to learn Japanese characters that I have seen. There are a great number of systems that promote learning Kanji by associating them with a visual image, which can be effective, but also has draw backs. A phenomenon common to any serious Japanese learner is the ability to recognize Kanji when seen, but when it comes to writing them... you draw a blank - or make subtle, but important mistakes.
Heisig, on the other hand, uses "imaginative memory" not visual, and this makes all the difference. Often I found that the opposite of the above scenario was true in the beginning stages - I'd remember how to write a character before I recognized it printed somewhere. And the best thing about this system is that it reduces the amount of time required to become proficient from a matter of years to a matter of months. I whole heartedly recommend this book to any and all Japanese students frustrated with learning Kanji!
I couldn't agree more.
Finally, for carrying around, a "denshijisho" (electronic dictionary)
is an absolute must. Although there are many brands, the ones I've
found most useful are the Canon Wordtank series. The current
thin-paperback sized IDX-9600 and IDX-9700 are excellent, featured a
jump search that takes you right away to the readings and compounds of
unfamiliar characters you encounter anywhere else in the dictionary. I used
to carry the earlier (similar sized, fewer entries) ID-6500 when I lived
in Japan, but it was just a bit to big to be handy. Canon now makes an
IDC-310, which is thick-creditcard sized, and I just bought one last
night. It has the same number of entries, a smaller screen an keyboard,
and slighly less functionality, but it's great to have something that
fits easily in the pocket. I found the following information on the
web, courtesy of Lynne Donaldson
My Canon Wordtank IDX-6500 portable electronic dictionary (denshijisho), bought about 16 months ago, seems to be on its last legs, so I've been researching the market for a replacement and upgrade. (I'd often wished that I'd splashed out and bought the higher-spec model in the first place.) I knew that the Wordtank series had the reputation of being the best electronic dictionary for non-native Japanese speakers, but I wanted to be sure that nothing better had become available in the last few months.
The Wordtank upgrades I was looking at were the IDX-9600, the IDX-9700 (identical to the 9600 except that it also contains a katakana dictionary) and the newer IDF-3000. The two IDX models are operated in almost exactly the same way as my existing denshijisho (which incidentally is still advertised in Canon's brochures, despite being something of an antique these days), but the IDF has a higher spec and is operated differently. These all cost between %15,000 and %20,000, though their official prices are higher.
I've also looked at several other models, including the Sony DD-IC200, the Sharp PW6000, the Casio XD-S700 and the Seiko SR750, all in the same price range. I discounted the Sony pretty quickly because its kanji dictionary doesn't seem to have any way of looking up kanji compounds. The others all allow me to do what I want to do, but only in a convoluted way. For example, if I'm looking for a Japanese word and the E-J dictionary offers several alternatives, the readings of which I don't know, I have to make a note of the kanji for each possibility, and look it up in the kanji dictionary using the stroke count method. Having found the initial kanji I have to page through all the possible compounds using that character until I find the compound I'm looking for, then I can look up the furigana (reading). Now that I have the furigana, I can go to the J-E dictionary, enter the furigana and see whether the translation that it comes up with fits the sense of the word I was looking for in the first place. This isn't such a problem for Japanese people, since in most cases they already know the furigana so they can skip the kanji search stage, but for non-native speakers it's something of a headache. With the IDX series, in comparison, you can highlight one of the translations in the E-J dictionary and jump directly to the kanji compound entry, which in this series is combined with the J-E dictionary, so you get not only instant furigana but also an instant English translation! (The IDX series also offers an English-language display option, though my ability to read Japanese is now at the stage where this is a luxury rather than a necessity.) In the other dictionaries, if the kanji compounds are defined at all in the kanji dictionary (and they aren't in the PW6000) then the definitions are only in Japanese. Some of them have jump functions but they're very limited in how they can be used - in most cases you don't seem to be able to highlight Japanese words at all, only English ones.
I eventually (we're into February now but I'm keeping this topic all in one place) decided against the IDF-3000; it has an excellent specification, probably far more than I will ever need, but isn't quite as simple for non-native Japanese speakers to use as the IDX series is. Besides that, there doesn't seem to be any way to find a kanji compound by looking up any character other than the first, whereas with the IDX series it's possible in some cases to start with the second (or third) character, albeit by a rather roundabout route.
So that brought my choice down to the IDX-9600/9700... but then I noticed that the much smaller, lighter and cheaper IDC-310 (also a Canon Wordtank) had almost exactly the same spec as the 9600, with the exception of a world clock replacing the 9600's travel English function (basically an English phrasebook for Japanese speakers, as far as I could see, so that wasn't something I anticipated making much use of anyway). In fact its kanji dictionary was billed as having roughly twice as many entries as the 9600's!
Of course, the reduced size of the IDC-310 - it's about a third of the weight of its bigger sibling - means a more fiddly keyboard and a smaller screen. For example, in the kanji idiom dictionary there's only room for four kanji compounds per screen rather than six, so paging through to find the kanji compound you want can take a long time. The compounds are listed in kana order, as with the 9600, but unlike the 9600, the listings also include compounds where the kanji you are searching by is not the first character. For example, if you looked up the kanji for study (gaku) and then listed the idioms for that kanji, "igaku" (medicine) would be listed on the 310 but not on the 9600. While this increases the length of the list you have to page through, it also allows you the option of searching by the second/third character instead of the first - useful if you can't locate the first character, or if you know that it's going to have hundreds of compounds listed. (Presumably this is why it's billed as having about twice as many entries in the kanji dictionary as the IDXs. There are probably actually the same number but you can look them up from any of their constituent kanji.) Also, the 310 (unlike my old model, and presumably also the 9600 though I didn't check) tells you how many pages of compounds there are in total, and you have the option of paging backwards and starting with the end of the kana alphabet if you so choose. (The entries are listed in kana order, as I said before, but all the single-character words come first, followed by the two-character ones, and so on.)
The "jump" function is more limited on the 310 than on the 9600, only allowing you to jump to a single kanji rather than a kanji idiom, but it's still a lot simpler than with the other brands. I've also found that for some reason you can't use the jump function to jump from a screen that you've reached via the kanji dictionary, but it does work if you go to the same screen via the J-E dictionary.
In the end I decided that, for me, the smallness, lightness and cheapness of the IDC-310 (it cost a little under %10,000, compared to %15,800 for the IDX-9600), combined with the ability to look up kanji compounds by the second or third characters, outweighed the smaller screen and the reduced flexibility of the jump function, and so I opted for that one. Incidentally, it seems that the instructions for this model are available only in Japanese, although it does offer the English menus as on the IDX series.