Looking for...
 

... an app which would bypass my school's firewall. Hopster is nice but it won't allow ICQ to get around the firewall...

You can tunnel ssh through if they haven't blocked port 22. www.anonymizer.com and www.cotse.net sell proxy service. If you're clever and you don't care about being anonymous (just want to get past the firewall), you can set up a system at home to do the forwarding (assuming you have broadband of some kind).

Just remember that your school's system admins are not stupid, and if they really want to spend the time and effort necessary, they _will_ find unauthorized traffic.

The trick is to keep your offenses small, inoffensive and (in particular) not likely to draw the wrath of the Copyright Fairies.

Consider approaching the admins and asking if they can open up whatever port ICQ runs on.

VSP, it isn't just that easy.
Over here we are in some kind of boarding school. About 800 people all having free internet. Most of them do use hopster because otherwise they couldn't use MSN-Messenger because the DoD don't allow it.
Actually Hopster does work fine but I cant get ICQ running on it. So if I only want ICQ running on my PC and not some downloading there shouldn't be a problem