bib-site
This is a set of PHP scripts which provide an interface to browse and edit a .bib file. Everything happens in the .bib file - no SQL database or anything like that needed.
Even if you don't need that, you might like bib-parse.php, which does a better job of parsing .bib files (or at least, my .bib files) than any other PHP parser I found.
I use this to run read.somethingorotherwhatever.com