A few months ago I was looking for a free computer algebra system (CAS). For some reason (probably I wasn’t really looking hard enough), I didn’t find anything that the bill.
Yesterday, while updating Cygwin on my Windows box at work, I saw a link to something called Mathomatic.
I turns out that Mathomatic is a nifty console based computer algebra system (follow the link and you can try Mathomatic via telnet).
The Mathomatic page includes a link to Maxima, a descendant of DOE Macsyma. Maxima is a more complete CAS then Mathomatic, but is a little more complicated to install.