Yeah, you need a proxy.
there is a huge list at tehbox.com/proxy, but it is blocked by most schools, as are most anonymous surfing sites and sites that show a list of proxies.
There are two types of proxies, cgi-proxies (operate through a script, dont have to mess with any browser settings), and there are regular proxies (machines that you directly connect to get on the web).
If your schools admins are dumbasses, you should be able to access the internet options fairly easily. If you can, go to the connections tab, and uncheck 'connect through a proxy' if it is checked, or if it isnt, type in the info you got on the site above. Just make sure you change the settings back when you leave, or you could get caught.
This only works on filtering software outside of your computer thats installed on the server (I know Bess is one), and wont work if you have a content filter. (software that searches a page for words such as porn, penis, etc. IE netnanny and some others).
If you have a content filter rather than a domain blocking system, your out of luck, unless you can gain access to an administrator account, or you really know what your doing.
If you want more info message me, I can tell you as much as you need
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(Ross)
SRMC
cBf