Have some time to kill?
Some fun word games:
Weboggle (play Boggle against others, on a 4x4 or 5x5 board)
Word Mojo (Yahoo, single-player Scrabble-type game)
Word Racer (Yahoo, like multiplayer Boggle on a large board)
Letters (enraging typing fun)
Etymologic (choose the best word origin)
Weekend Edition's Sunday puzzle (Will Shortz's NPR challenge)