Plumber's Nightmare - connect the pipes to leave no gaps. There are 60 levels and it's great when you have a few spare minutes.
My webOS Apps - Very easy way to keep track of your app sales and statuses. Great for webOS developers!
TweetMe - Beautiful Twitter client that's very functional. Just look at those screenshots!
Sports Live! - A great way to keep track of your favorite US sports. Lives in the notification area so you can always know what the score is. There are also cheaper versions available for individual sports - I have the baseball one myself.