Activecollab.com is a free open source online project management script written in PHP. It is blindingly good, written by a Serbian web developer called Ilija Studen.
This guy is going places, and so is AC. Its not a website, its a PHP engine that can be installed on any server running PHP5.
It just does it all and already there seems to be a great little community sprouting up on the forum.
I have already setup some projects and have been messing, Its very intuitive and very powerful, that's the ideal combination. I have set it up for some small projects in work with a few of our developers and designers. There is no manual yet, so that shows how easy it is.
Not the most exciting of posts i have ever made, but AC really could be the Ubuntu of project management.
Peace, freedom and bandwidth.