JabRef is an open source bibliography reference manager. The native file format used by JabRef is BibTeX, the standard LaTeX bibliography format. JabRef runs on the Java VM (version 1.5 or newer), and should work equally well on Windows, Linux and Mac OS X.
JabRef continues to be an excellent bibliography manager.
Using BibTeX as the master database and JabRef to populate, manage, and export from it has been really nice. The key has been letting Emacs manage the keys and sorting.