This little TweetCC Twitter App makes it very easy for you to license your tweets, according to any of the various flavors of the Creative Commons License. All you do is press the button by your chosen flavor of creative commons, it tweets the appropriate message as a reply to @tweetcc, and then they will link to your twitterstream on their webpage.
Only about 400 people were in it when I signed up, (their first day), and at this writing it has doubled. I chose attribution noncommercial share-alike. BY.NC.SA flavor means: you may use/remix/derive from my twitter profile without asking permission as long as I get a link back, it’s noncommercial and you agree that anyone who remixes any part of your work that’s derived from my work must license it under these same terms. I don’t like the idea of someone profiting off my twitter stream without sharing the money with me. It’s a long shot but some day some clever person with more marketing savvy than I have will figure out how to aggregate twitter streams into some crazy-assed concoction that makes money. If I had any idea what that concoction would be I would build it myself, but I’m not coming up with any brilliant ideas.