Words In Space, a very fun and addicting game from HitPoint Studios, is available for iPhone, iPod Touch, and the iPad.
A very simple premise, letters(designed as asteroids) drop from the top of the screen and you have to make as many words as you can as quickly as possible. The bigger the word, the higher the score! But don't wait for just the right letters to fall to make your perfect word. If you delay too long and the asteroids/letters pile up you will lose your shield and your game will be over! 
Buy it here for only 99 cents! Well worth the money for hours of fun. 