Open Source IM and voice client using Jabber and SIP protocols, with great audio quality thanks to speex and a nice and clean interface. Programmed in Java and C++. It supports chat, voice and file transfers.
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).