I cant believe no one has said to connect to a remote linux box through xserver and view websites from there.
xserver ports are blocked you say? change the config on your linux server to run xserver on port 80 :-).
Even the admins asked me how i did this, so they could check on their email from home.
EVEN BETTER: turn ssh tunneling on your xserver and now not only have you got out of the proxy problem, but they cant read ANY of the tcp/ip or udp traffic you send to that server because its all encrypted.