On-Line Jigsaw Puzzles
Most of these sites will play right in the web browser you're using now. Features of most include and automatic "solve", hints, preview and level of difficulty. You will need to have the Shockwave plug-in installed for many to work.

Jigzone
The Jigzone has many online jogsaw puzzles from easy to very hard. Geat Site!

On-Line Puzzles
DLTK's Crafts for Kids has a jigsaw section.

Puzzle House
Free On-Line Puzzles, Easy Medium and Hard. Lots to choose from.

Shockwave Gallery Jigsaw Puzzles
A great selection of puzzles in many categories.