Open Source Math Software
I used Matlab quite a bit in engineering school and got used to having it available not only for math but for its programming ability. After graduating there were times I wished I had access to Matlab but didn’t couldn’t afford the commercial license so I looked for open source/free software with similar capabilities and was really surprised to find some great software.
GNU Octave – Similar functionality and programmability of Matlab. Programs written in Octave can be run in Matlab if they are written with that ability in mind.
FreeMat – Another app similar to Matlab – I personally used this one more than Octave – not for any particular reason I just liked it. The programming language syntax is similar to Matlab.