When I was looking for a bit of relaxation, I tried to find an open source, cross platform Jigsaw Puzzle application. That led me to sphaero, which largely did what I was looking for.
I couldn't resist hacking on it a bit. I've kept the heart largely unchanged - the general cutting of pieces, the main puzzle class, and the basic image handling and display. It's been refactored a bit, modernized (so it needs Java 5 or later), cleaned up, and the user interface has been tarted up significantly. To be honest, the basic core was pretty darned good already, the interface just deserved a little extra TLC.
You can also just grab the jar file;
depending on your browser and operating system it may run straight
off. If not then just feed it to java -jar, or just run
the sphaero2 script from the main download (which includes
all the source).
If you have Java installed, click on any of the images below to try the Java applet version.
(I tried emailing Paul Brinkley, the original author, but that bounced. So I can't thank him personally, but Thank You Paul! And if you want to get in touch, my address is on the site here.)