JabRef is a reference management software that uses BibTeX as its native format. JabRef provides an easy-to-use interface for editing BibTeX files, for importing data from online scientific databases, and for managing and searching BibTeX files.
Website to download: http://jabref.sourceforge.net/
Pybliographer is a reference management software tool that deals with bibliographic databases, used for viewing, editing, searching, and reformatting bibliographies. Written in Python and licensed under GNU GPL, it provides a scripting framework of classes and functions, which makes it extendable to many other applications.