ReadWriteWeb has an interesting article about How Twitter is Changing the World of Professional Poker. Professional poker players are using Twitter during tournaments, commenting on the game as well as providing information about themselves and their intensions. But just as in the game of poker they might be bluffing.
The article mentions PokerRoad as a site that uses information from Twitter.
As example of a professional poker player that uses Twitter they mention Doyle Brunson, @TexDolly. There are more professional poker players on Twitter, like Gus Hansen @gus_hansen.