JabRef is the true open source bibliography reference manager. It uses BibTeX as his native format. It is a wonderful editor of BibTeX files allowing you to perform several actions when dealing with such files. Just a couple of them: import BibTeXML, CSA, Refer or Endnote, ISI Web of Science, SilverPlatter, Medline or Pubmed (xml), Scifinder, JStor and RIS, OVID, INSPEC, Biblioscape, Sixpack. Export HTML, Docbook, BibTeXML, MODS, RTF, Refer or Endnote, OpenOffice.org, manage, search through BibTeX files. Program runs on Java and works with Microsoft Windows, Linux and Mac OS X operating systems. If you're looking for a cross-platform BibTeX reference manager, JabRef is the perfect tool.
If you need a graphic application for your bibliographic databases - this is the software that you were looking for. This program is designed for BibTeX databases but it can help you to manage other bibliographic formats too. You can use it to export to a wide range of different formats and if you need to, you can custom (write) your own export filters. Use JabRef if you need to search a pattern in the whole bibliography or to group entries by keywords and other fields, add your own fields to any BibTeX entry type and many other tasks.
This software has many other features and is probably the best free bibliography reference manager. You will need Java 8 (or newer) installed on your machine to run this application.