A1 Puzzles
Offers interactive crosswords, sudoku, trivia, jigsaw puzzles and more. With regular contests with money prizes.
http://www.a1puzzles.com/

The Puzzle Museum
The home to the World's finest collection of Mechanical Puzzles; also known as Chinese Puzzles, Puzzle Objects, Mechanical Puzzles, Real Puzzles, and Practical Puzzles from 320 BC to Tomorrow's prototypes.
http://www.puzzlemuseum.com/