Axiom The Scientific Computation System see http://axiom-developer.org/index.html
This package for computer algebra uses the methodology of LiterateProgramming (see http://axiom-developer.org/axiom-website/documentation.html )
Axiom started off with IBM as Scratchpad. It was renamed Axiom and sold to NAG who have now allowed it to become open source (see http://www.nag.co.uk/symbolic_software.asp)
I am very puzzled that I had never come across it before. -- JohnFletcher
To those of you on Windows: Before dragging your nuts across the cheese grater that is http://axiom-developer.org/index.html "Axiom on Windows", try http://www.cygwin.com/ (CygWin) first for the X server AND build tools.
(And we luv the hand-written HTML website on screaming yellow background, too!;)
Can it do MatroidTheory?