I am recruiting agressively people to try the new KAlgebra. Its in a beta state, things work but there may be some issues.
It has been tested in GNU/Linux (KUbuntu being precise), Mac OS X and Windows XP SP2. Yes, now it is really multiplatform. 🙂
To compile and use it you need to have Qt4 libraries (both execution and development) and a subversion client (subversion package on linux and tortoise svn in windows. On macos I used the same in linux, but it behaved in a strange way).
To download it and compile follow the next steps (unix way, other systems may differ the commands but the idea is the same):
mkdir kalgebra
svn checkout svn://svn.berlios.de/kalgebra/trunk
cd trunk
qmake-qt4
make
Hope someone tries it, and if you do, please tell me about your experience :).