In some of my posts I have mentioned the ChessDB chess database program, but you may also want to use one of the other free available chess databases.
Scid (Shane’s Chess Information Database) was written by Shane Hudson. He started Scid in 1999, but the development stopped in 2004.
December 2006 the development of Scid continued with the publication of the first release of ChessDB. This project was started by Dr. David Kirkby.
Pascal Georges joined him, but the cooperation went very wrong and he started another continuation of Scid. The two different points of view can be found here and here (link unavailable, but Shane added Pascal Georges as admin and Pascal continued with Scid).

In addition ChessX is another free chess database under development. Initially ChessX also has started as a continuation of Scid, but after some initial development, it was decided to break away from the Tcl/Tk code and start to program in Qt and C++ in order to get the program faster.

Another free chess database is Jose, but you can also use the free versions of some of the commercial chess databses. Chess Assistant Light is the free version of Convekta‘s Chess Assistant and ChessBase Light 2009 is the free version of ChessBase. Chess Assistant Light is limited to 15,000 games and the games are limited to 255 moves. ChessBase Light is limited to 32,000 games per database.

You just have to look and decide for yourself which (free) Chess database will be the best.