TortoiseSVN - The coolest interface to (Sub)version control
TinyCat - The online catalog and integrated library system for tiny libraries, powered by LibraryThing.
SnailSVN - Similar to Tortoise SVN for Windows but integrated into Finder
Koha - Koha is the first free and open source software library automation package (ILS).
Xversion - Super easy enterprise class version control.
DSpace - DSpace open source software enables open sharing of content that spans organizations, continents...