To be effective over the long haul (i.e. to avoid burnout) you've got to laugh often, laugh hard, and laugh at yourself. And oh yes, laugh at your enemies too. In that spirit the sites below are advised.
Adbusters - Ridicule is one of the best non-violent weapons available, and the Adbusters folks are masters of it. Poking fun and questioning our consumerist lifestyle on a regular basis is what they do better than anyone else.
This Modern World - Tom Tomorrow consistently offers some of the funniest and most intelligent cartoons anywhere, that also inform us of the burning issues of the day. Check him out!