Help! I'm addicted to Fermat's Fences, a new logic game by Everett Kaser.
Every time he posts a new game, I end up spending the next week playing every level. They're just nice simple logic puzzles, and a great pastime. I'm not sure which has been my favorite, but I especially liked Honeycomb Hotel, Latin Squares, Knarly Mazes, and Watson's Map.
[Update 11/18/07: finished all 100 puzzles… that's just ridiculous]