RefDB is a reference database and bibliography tool for SGML, XML, and LaTeX documents, sort of a Reference Manager or BibTeX for markup languages. It is portable and known to run on Linux, Free/NetBSD, OSX, Solaris, and Windows/Cygwin.
Emacs Photo Database provides functions to manage a collection of photographic films, negatives, and prints stored in a SQL database. It is targeted at fine-art photographers and other people who use a wet-process workflow instead of digital imaging.