Koha - Open Source Integrated Library System
http://www.koha.org/

Koha is the world's first Free/Libre Open Source Integrated Library System. Originally made in New Zealand by the Horowhenua Library Trust and Katipo Communications Ltd, the Koha system is a full catalogue, opac, circulation, member management, serials, and acquisitions package. This has been added to the tools section of Research Resources Subject Tracer™ Information Blog.