MantisBT is a free popular web-based bugtracking system (feature list). It is written in the PHP scripting language and works with MySQL, MS SQL, and PostgreSQL databases and a webserver. MantisBT has been installed on Windows, Linux, Mac OS, OS/2, and others. Almost any web browser should be able to function as a client. More info »
devZing provides MantisBT as a hosted service for those who don't want to manage servers and just want to get things done. http://www.devzing.com/mantisbt.php
