BMM's Scrabbler
Generate words based on TWL/SOWPODS. Good for Scrabble and anogram games.

BoLS Boardgames - Scrabble New!
A Scrabble helper site with several online tools, including an anagram solver, a dictionary lookup, along with tutorials and rare word lists.

Hotspots Word Game
A word game similar to Scrabble and Yahoo! Literati, that will help you learn countless words. Numerous configuration options include letter frequency, tile values and board design.