Hah, my company does that as well and quite often I find the need to circumvent their security measures. What I've done is used a program called "redir" (Search the forum and you'll find out how to use it and the link) and I redirect it to the local port of SQUID. I've also instaled squid_auth, so I must pass my login/password to the system to gain access to the proxy (This enables me to avoid being an open proxy). I then configure my browser to use that proxy server.
I'd set it on a high port like 57600 or something.
Hope this helped,
Nathan