In my previous post, I put in a big plug for people setting up tor relays to help those in Iran browse the web anonymously and evade censorship. What I didn't mention is that installing Tor on a Windows desktop machine is apparently very easy.
There is a very nice blog post describing exactly how to do this over at Ian's Brain.
Update: Ian Souter's site is down at the moment. The information he posted about Tor is cached on google.