There was a filter called Websense on the network for the entire school system at my old schools and I found a little tiny program that got around it and it worked flawlessly. The program is called Ultra Surf and it was developed for use in China where the internet is government controlled and filtered. The program is an exe so if the computer allows them to run you can get through the filters. It works by encrypting the data before it leaves your computer, sends it to an Ultra Surf server for decryption, and then forwards the packets to the site your going to. Myspace, Facebook, Youtube, everything worked when I used it. Also, my connection sped up significantly, probably because the firewall could did not scan the packets because they were encrypted.
Hope you have the same success with it that I did!