Here is a great talk from the Chaos Communication Congress about Tor and censorship: lessons learned. It's the inside scoop from the Tor guys on how they're keeping Tor usable inside China, Iran, etc despite attempts to block it.

If you're like me, you have resources and would like to help Tor, but the exposure of running a exit node is way too high, and even running an non-exit node seems risky. Now there's a third option, running a bridge which can be used to get to the Tor network.

The great thing about doing this is that you can be pretty sure anyone using your Tor bridge is the kind of person you want to help (and not some spammer or worse). There's little reason to use a Tor bridge unless your ISP/Government is repressing you. Also, the worst thing that is likely to happen to your bridge is that $COUNTRY discovers its IP and blocks it. So the benefits seem focused and high, and the risks easily managed.