Actually, I know of at least one school that DOES block everything but HTTP. Well, sort of. They actually block every port except for port 80. Even then, some protocols are blocked (like AIM). I've had quite the adventure these past eight weeks trying to get around the limitations. Fortunately, some awesome people started up
http://www.meebo.com/ for my IM needs, and Gentoo includes emerge-webrsync as an alternative to emerge --sync.
Still, it's terribly annoying. If my home university did the same, I'd seriously consider moving off-campus. Students pay a large sum of money to live in the dorms and apartments provided by the University (~$6k/year). Part of that money goes toward funding the Internet connection. At the moment, the only type of traffic that they throttle is streaming video. That's enough. I don't need my games throttled, too.