MAPLE

• Official Maple Documentation from MapleSoft
• Maple Introduction as Maple Worksheet (mws, 67KB, 22 pages)
  To read this, save the file MapleIntro.mws (just opening it with your browser will make it look like gibberish) and open that worksheet with Maple V or higher.
• You can also download the same introduction as a PDF File (pdf, 340KB, 26 pages)
• Wikipedia:Maple
• WikiBooks:Maple

MATHEMATICA

• Official Mathematica Documentation from Wolfram
• Wolfram Demonstrations Project
• Wolfram Education Portal
• math.fullerton.edu/mathews/N250L/MathematicaTutorials.html (Mathematica Tutorials)
• Wikipedia:Mathematica
• WikiBooks:Mathematica

MATLAB

• Official Matlab Documentation from Mathworks from MathWorks
• www.math.siu.edu/matlab/tutorials.html (Matlab Tutorials)
• Wikipedia:Matlab
• WikiBooks:Matlab

GAP - Groups, Algorithms, Programming

• Gap Overview
• Gap Documentation
• Wikipedia:GAP

Others

• Pari - computer algebra system designed for fast computations in number theory
• LAPack - Linear Algebra PACKage
• WikiPedia:LaPack
• BLAS - (Basic Linear Algebra Subprograms)
• WikiPedia:BLAS