I have been successfully using Twitter for the last six months to promote a website that makes me a little money each and every month.  I am planning on building another one soon now that I am learning how to promote it.  I have learned that the trick to using Twitter is to build a relationship with your followers.  Of course you have to build a following, but you want them to pay attention to your tweets.  I have found a portal that offers twitter flash games.  I simply tweet the link and tweet my scores.  My followers do the same which builds a stronger relationship between us.