Related links on the internet

Other freely available math packages that have symbolic capabilities

This is a short list of links to other related math packages I could find on the net for which source code is also available. If you know of any other software please let me know.

Ginac
Ginac is a c++ library for doing computer algebra. It allows symbolic manipulation from within a c++ program. It is currently in active development, and looks very promising.

GiNaC is an iterated and recursive acronym for GiNaC is Not a CAS, where CAS stands for Computer Algebra System. It is designed to allow the creation of integrated systems that embed symbolic manipulations together with more established areas of computer science (like computation- intense numeric applications, graphical interfaces, etc.) under one roof. It is distributed under the terms and conditions of the GNU general public license (GPL).

HartMath
HartMath is a computer algebra system written in Java. All math functionality is written in Java itself. HartMath has roughly the same functionality as Yacas.

HartMath is an experimental computer algebra system written in Java 1.1.

Some of the main implemented features are

Big rational number arithmetic, symbolic differentiation, linear algebra functions, 2D plot functions, numeric computations, pattern matching transformation rules, functional programming, pure functions, runs on EPOC32 (i.e. Psion 5mx with Java virtual machine, ...)

Pari-GP
Pari-GP is somewhat similar to Yacas, but based on pure "C" code and it is geared to Number Theory while not being actually "symbolic". That is, all expressions are expanded completely. (1+x)^2 = 1+2*x+x^2 and is not stored in the unexpanded form. Also, no LISP or equivalent is included. More details are available on the web.
Jacal
JACAL is an interactive symbolic mathematics program. JACAL can manipulate and simplify equations, scalars, vectors, and matrices of single and multiple valued algebraic expressions containing numbers, variables, radicals, and algebraic differential, and holonomic functions.

It is written in Scheme, and has the GPL license.

Maxima
Maxima is a Macsyma (early computer algebra system) clone, fully GPL'led. It can be found in the GNU repositories, and is written in Common Lisp. Maxima is being maintained by Bill Schelter.
MockMMA
MockMMA is a Mathematica-style parser and pattern matcher, written in Lisp, with some additional mathematical functionality. The link mentioned here directs you to Richard Fateman's page, which should contain a link to MockMMA.
LiDIA
(review forthcoming)

Various other mathematics-related software

Octave
(review forthcoming)
yorick
(review forthcoming)
scilab
(review forthcoming)
rlab
(review forthcoming)
Object oriented numerics
(review forthcoming)
Gnu Scientific Library
(review forthcoming)

Miscellaneous

ffes
Written mathematical expression reader. (review forthcoming)
Operations-Research objects
(review forthcoming)

Free documents relating to computer algebra

This is a short list of links that might be of interest, regarding CAS algorithms.
mathworld
(review forthcoming)
Wester benchmark
The Wester benchmark has been used to compare features between various CAS.
Known math
(review forthcoming)
A=B
(review forthcoming)