If you do, you will love this site:
The things I like about it are that it runs entirely in a browser and is therefore platform independent, they don't ask you to register in order to do anything on the site, and if you want you can create your own puzzle from your own picture collection.
If you like jigsaw puzzles then this is very addictive.
Translation for the younger members : A jigsaw puzzle is what old farts play instead of first person shooters or online multi player rpg's. If you are still confused, then next time you are forced to pay a visit, ask you granny, she is bound to have one to show you.