TargetProcess: Planning is a web project management software aimed at agile project management. It's also free to download (built for asp.net). It looks pretty cool and seems to contain most of the features needed for an XP project to be managed. There's also a nice Agile-minded blog on the site.
However, one thing always worries me: XP supports the notion of "Use the most basic and simple tools to manage and get feedback". You know, stuff like white boards, paper, cards. Perhaps, in a sense, managing it using software, be it agile-minded and all, arn't you still denying the whole notion of ease and simplicity? software itself makes the whole process more complex and harder to track. Will this software produce the daily meeting output on a white board? No. Will it produce a project plan on a wall with cards? no. You still need to do that plus manage the whole process on your software. Be it MS project or something specifically designed for agile projects - arn't you slowing yourself down and bogging your project with unnecessary complexity? COuldn't you do just fine without it?
The answer I would guess depends on the project. for me, filling out user stories from cards into my computer already sort of defies the whole idea of being able to tear it easily and redo it from scratch. You'd have to essentially do it twice -once physically and once with the mouse. The more I think about it the more I think it Will be hard to adopt such a thing.
Think about it, you're essentially saying "Manage the new way of doing things using the old way of managing things", arn't you?