Wow, I'm really pleased with the reaction to the Green Tweeting RSS feed idea. This could be something I build for a while. Riomix steered me toward a post on Digg I'll have to look at.
Of course, there are a couple of other places one can find a whole host of environmental discussion - I like the Environment Room at FriendFeed (administered by Chris Baskind and SpostareDuro) and EcoTumble. My goal was to see if the discussion happening exclusively on Twitter was a little different than other places. More on that later.
Meantime, I've added the following tweeters to the RSS feed:
I have a few more I need to get to when I have a little time. I'm also considering putting together similar feeds for other distinct communities - now that I have the hang of pipes (at least for this sort of thing), it's not difficult...