All platforms (with the Java runtime): Free software MeD's Movie Manager is not as feature-rich as heavier-weight media managers like Griffith, but it still makes tracking your movie collection on your computer desktop easy. Catalog the movies you own, pull film info from IMDB or TV.com to fill in missing media information, and retrieve cover art. The program comes with multiple skins to customise its appearance, too. Two strong features include support for television series via the TV.com database and the ability to scan directories to retrieve movie file names, which saves you a lot of data entry hassle if you store movies in digital format. Here's a screenshot of MeD's in action.
MeD's Movie Manager a free download for any platform with the Java runtime 1.4.2 or later. Thanks pino227!