If its anything like the IT dept that I work in, we block in the PIX firewall by ip address if we really don't want you going there. not many ways to get around that.
I think your best bet is using a VPN service. Try http://www.hotspotvpn.com/ for free and see if it works. It will cost you money though, but it's cheap. I'm not sure how to get around Websense if that's what your company is using.