Word games are probably my least favorite genre on the App Store at this point -- I think they're overused, and many companies these days are just kicking out half-baked spelling games in the hopes of reaching a large casual audience. But Letter Rush, put together by a former Zynga studio, is different enough that it's worth mentioning: It's a word game that will probably make you better at word games.
Most word games give you a set of tiles and ask you to spell words with them, and Letter Rush does that as well. But this game also gives you the words to spell, as they move across the top of the screen towards the left. That makes it a much different game than usual -- it's more about learning to spot words than actually spell them. And it could even teach you to be better at word games, to look for ways to spell certain words that might not be readily apparent at first.
The goal is to spell all the words on screen before they hit the left side, but you do have a few extra powerups helping you out. Occasionally, words will have blanks in them, and in that case you can use any letter in that spot (though that sometimes backfires, as it appears the word still needs to be legit, so there may be only one letter that fits in that space). And sometimes you'll get a bomb letter tile, which when used will clear the entire board for you. The game is essentially endless, but when words reach the far side of the screen, it's game over.
Letter Rush is an interesting take on the oft-visited word game genre, and it's different enough that it's worth a look even if you're bored of spelling games on the iPhone. Letter Rush is available as a free download right now.