Login is available for some of these games to log your score but where it is available it is not required.

Link 1: DeepLeap: The Fast-Paced Time-Wasting Word Game! [Demo: Under development but playable]
Link 2: Cryptograms - Play Online or Print Your Own for Free!
Link 3: Etymologic: the toughest etymology (word origin) game on the Web
Link 4: Knoword | Expand your vocabulary!
Link 5: Herd a Word