This is an 
interesting thread on slashdot this morning talking about software
to do symbolic math. Tom and I have been using R a lot, which is mentioned, but R really can't do symbolic math very well. A bunch of other packages that I haven't heard of before, including Maxima. Worth a look. Maxima is available through fink.
This is pretty funny. Back in 2000, peacefire wanted to see if personal, homegrown sites were treated the same as large organizations by the blocking software companies. They found that they were not. They created some personal webpages that had quotes taken from a bunch of well-known conservative sites that constituted hate speech. They then contacted the blocking companies to complain about the sites. In every case, the sites were blocked. Afterwards, they contacted the companies to ask that the large organizations' sites (from which the original quotes had been drawn) be blocked as well. In every case, the companies refused to block those sites.