BrainsBreaker (Popularity: )
http://www.brainsbreaker.com/ Potentially thousands of pieces. Save feature. Organizational options. Allows turning puzzle into any image. Windows shareware.
Puzzelate (Popularity: )
http://www.puzzelate.com/ Solve puzzles against the clock. 30 images included. Supports JPEGs. Free trial. For Windows. By Squirrely Productions.
Jigsaw Reality (Popularity: )
http://www.dreamcode.com/ A game using 4 to 900 pieces using player chosen images. Offers screenshots, trial download, and purchasing information.