MantisBT is a free popular web-based bugtracking system written in the PHP scripting language. The most common use of MantisBT is to track software defects. However, MantisBT is often configured by users to serve as a more generic issue tracking system and project management tool.

Features:

event-driven-plug-in system

works with MySQL, MS SQL, PostgreSQL, SQLite, Oracle and IBM DB2 databases

RSS Feeds

Customisable workflow

Wiki integration

Chat integration