Below is a list of puzzle websites we enjoy and appreciate, in no special order.
Mazelog - interactive and original logic mazes, includes a monthly competition;
PuzzlePicnic - A place for people who love logic puzzles -- such as Hitori, Kakuro, Alphametic, and much more;
The Griddle - weekly updated blog with new and classic puzzles authored by David Millar;
Puzzles and Brains - they offer more than 3000 printable japanese logic puzzles -- such as Masyu, Hidato, Numbrix and Slitherlinks -- if that's your thing.
Puzzle Prime - A ad-free website featuring brain teasers, detective mysteries, logic games, and much more.