PLEIAS is an open-source Inter-library Loan System (ILL) written in PHP-Mysql. Some of its major features are: custom workflow and account types, customer and supplier financial monitoring, group accounts, customer web interface for order tracking.
OPACIAL is an open source Web 2.0 Online Public Access Catalogue (OPAC). It is based on PHP-Mysql (requires Yaz and GD). The users can isnert their own social tags/opinions and have a faceted search/browse interface (also using social tags).