gCensus is a Linux, GNOME-based program designed to be a program to store, index and sort Census data, for either genealogical or historical purposes. It will support as many Census formats as we can add into it.
OpenAncestry is a genealogical management tool written in C. It has a GTK+ interface, and has a database plugin architecture. Currently, OpenAncestry comes with a SQLite database plugin.
Relativity is a free genealogical database program for Mac OS X.