I'll second rhari79's occupation with Tiny Wings ... very fun and addictive (and a pleasure to use/play!).
I, too, find myself addicted to word games. I play Words With Friends as often as I can (Mickey330 - invite me!) because of its asynchronous game play. I also enjoy Scrabble, Boggle and Ultimate Hangman (the "condemned" character interacts with the game play).
For less common games, I enjoy:
- Wordstorm: You get a wheel with one letter in the center and eight around it. You spell words and you must include the middle letter (can only use the letters once per word). Collect points based on difficulty/popularity of the word
- Cryptogram: Just like the newspaper's Crytoquips (which are hard to find, BTW). Very nice layout and good word game
- The Word Chase, Moxi and Moxie 2: Word building games. Hard to describe but fun to play.
- Jumble Classic: Because who can resist jumbled word puzzles?
These are the ones I play regularly, when I'm not playing Tiny Wings or TouchRummy (a very cool tile game based on the card game Rummy).
Hope these'll help give you some ideas.