Open Source Genealogy Projects
Open source tools for genealogy research, family tree building, and ancestral record management.
Gramps
Open source desktop genealogy program for building and exploring detailed family trees with full local data control.
Alternative to: 
Family Tree Maker
Family Tree Maker
webtrees
Self-hostable web-based genealogy application that turns GEDCOM files into collaborative family tree websites.
Alternative to: 
Ancestry.com
Ancestry.com