Lurker is a mailing list archiver designed for capacity, speed, simplicity, and configurability in that order. Noteworthy features include: google-style searching on all fields, chronology preserving threads, multilingual, and attachment support.
A simple yet very powerful and fast PHP website search engine. TSEP is built to index your site so it can be searched later within seconds. Features: stopwords, logging, MySQL boolean search, localized, CSS formatting. See www.tsep.info for more info
This forum software is a Java based discussion forum, that uses JDBC to store data in a database. This discussion forum is available in different languages and has features for easy integration into a site and easy administration of forum.