Typo: http://typosphere.org/projects/show/typo
Mephisto: http://mephistoblog.com/ http://github.com/technoweenie/mephisto/tree/master/db
Redmine: http://www.redmine.org/
Radiant: http://radiantcms.org (git: git://github.com/radiant/radiant.git)
Tracks: http://www.getontracks.org/ (git: git://github.com/bsag/tracks.git)
spot-us: http://github.com/spot-us/spot-us/tree/master
RailsDB: http://railsdb.org/ git://github.com/gdonald/railsdb.git
Insoshi: http://github.com/insoshi/insoshi/tree/master
xlsuite: http://github.com/xlsuite/xlsuite/tree/master
Find more at http://www.opensourcerails.com/