Comparison of Polynomial-Oriented Computer Algebra Systems -
By Robert H. Lewis and Michael Wester. Presented as a poster to the 1999 ISSAC Conference.
http://www.fordham.edu/lewis/cacomp.html

Computer Algebra and Problem Solving Environments -
Abstract for Stanly Steinberg's article in "Comparative CAS Reviews and Philosophy", suggesting 6 ways in which computer algebra systems could be improved.
http://math.unm.edu/~wester/aca96/Steinberg_abstract.html

Computer Algebra Benchmarks -
Collated by Computer Algebra Fachgruppe, Mannheim.
http://krum.rz.uni-mannheim.de/cafgbench.html

Computer Algebra Pages and Servers -
A collection of links.
http://krum.rz.uni-mannheim.de/cabench/cawww.html

Edu2000 Visual Algebra -
 Designed to ease the difficulties many students experience during the transition from arithmetic into the world of algebra using visualization. Covers linear and quadratic equations.
http://www.mathematicssoftware.com/mathematics-software-html/algebra-1-software.php

Felix -
 Computer algebra system for computation in commutative and non-commutative rings and modules. Win32, Unix.
http://felix.hgb-leipzig.de/

Fermat -
Computer algebra system that does arithmetic of arbitrarily long integers and fractions, symbolic calculations, graphics, and other numerical calculations. Free download. Documentation.
http://www.bway.net/~lewis/

FINITAS -
Discussion group for this package for the construction and analysis of finite algebraic structures such as loops, quasigroups, and groups.
http://groups.yahoo.com/group/finitas