Open source mathematical software!

For many years I have wondered why there was no open-source alternative to Maple, Mathematica and the like. The November 2007 Notices of the American Mathematical Society has an opinion piece discussing this and advocating such a thing. The authors are involved in producing just such an alternative, called SAGE. Written in Python, it seems very promising. It has interfaces to Magma, Maple, Mathematica, MATLAB, and MuPAD, and the free programs Axiom, GAP, GP/PARI, Macaulay2, Maxima, Octave, and Singular. Try it out!