There are several places which have readonly versions of sources available via http, alternatively there is a socks client or even htfilefs, the former uses the SOCKS protocol to tunnel through the firewall.
htfilefs mounts a remote ISO image (like the plan9 nightly build iso) over an http connection and expands it as a hierarchy. You could probably write some tunneling software to run on your home machine and work machine using http in between, but your corperate IT department might not see the funny side of such practices... -Steve