Tor would really be the best cause to donate bandwidth to. You can run a "middleman" relay if your host forbids proxies. Unlike an exit node, relays only connect to other nodes in the network and relay encrypted data.

The list of nodes is public however. If your ISP really is some sort of mecha-nazi that would actually go snooping around proxy lists, the alternative is to run a bridge server, which does not appear on any published list. These are accessed by people in countries that block all tor nodes. They send an e-mail to an address which replies with the key of a "bridge" node. These nodes act as a hidden first hop into the tor network

If you worry about the moral implications of transporting that kind of traffic, I recommend the following reading:

http://www.torproject.org/faq-abuse.html.en

The gist is that real criminals don't need tor, as they can achieve much better anonymity through criminal means, e.g. building a relay network out of zombies, stealing cellphones.

Also, here's the same info except written for someone who has just detected abuse coming from a tor node: http://gitweb.torproject.org/tor.git?a=blob_plain;hb=HEAD;f=contrib/tor-exit-notice.html

Notable sentence: "[...] the social need for easily accessible censorship-resistant private, anonymous communication trumps the risk of unskilled bad actors, who are almost always more easily uncovered by traditional police work than by extensive monitoring and surveillance anyway."