Pazaak Cantina is a free game (that is from the game Star Wars Knights of the Old Republic) in either played on the web or through a game download that is like blackjack with a twist. It's first to three in which you have to go to 20, not 21, and you also have a hand of cards to add or subtract to your current total. You can play against other players or go against many CPU rounds.
Give it a shot! You may become addicted!
http://www.pazaak.org/play