A powerful, cross platform, SQL database system
Firebird RDBMS offers ANSI SQL features & runs on Linux, Windows & several Unix platforms. Features excellent concurrency & performance & powerful stored procedure & trigger language. WEBSITE link is below, TRACKER is http://tracker.firebirdsql.org
cdBB [Coldfusion Driven Bulletin Board] is an open-source message board written using technologies like Coldfusion, XML and Java. It goals to be a complete open source enterprise solution for online communities.