A BiBTeX managing program, written in Java and licensed under GPLv3.
ReferenceGUI can search your LaTeX files for where the references are used, which references that are in use, and in general help you with typing in your references.
It can be downloaded on the the sourceforge project website.
Or by clicking here:
For Linux/UNIX/Mac OS X users, get the universal release and run it by : java -jar referencegui.jar
You might be able to run it on mac by double clicking on it, as the jar file has a MANIFEST file, but I dont have a mac so not sure..