A system for reporting, managing, and tracking bugs and other issues on multiple projects over the web. Admin is minimal; all that's required is a generic Apache + PHP4/5 box. Bug data are stored as native XML -- no database or mail server needed!
Kennwhite works excellent.
as promised, it just took 5 minutes to setup and get it running. (almost) perfect for my need. That almost was because I was expecting one more thing, users should be allowed to add more comments to a bug. e.g. scenario: the responsible developer adds a comment, what if another developer wants to add something to it. Apart from that it looks great!