There are a lot of programs to manage your references and some of them are capable of the BibTeX format (or are even programmed for that reason). A list of programs and their most important features is available in the LyX wiki. Some programs are also linked on the TeXnik webpage.
At first, I used Sixpack, which is no longer under development (since 2000). At the end of 2002 or beginning of 2003 I came across Nizar Batada's JBibtexManager, which was then at its very beginnings, but already quite promising. I translated the interface to German, and Nizar accepted a lot of my feature requests. In late 2003 Nizar merged his program with Morten Alver's Bibkeeper and the new project was called JabRef (
J for Java,
a for Alver,
b for Batada, and
Ref for Reference Manager—this is at least my interpretation). I did also the German customization for JabRef (though not longer on my own) and translated the help files into German.