PhotoDirectory is a cross platform (Java) application to organize digital photos. Great effort has been given to keeping these pictures in an order accessible without the need for any organization software - no databases are required.
PhotoDirectory was written using Java version 1.5 (commonly called 5.0 for some reason or another). You cannot run it on anything less than this. Depending on your system, you may need to explicitly state which Java VM to use. If you use Macintosh OS X, I include an application package that does everything for you. If you don't use OS X, now is a great time to try.