FogBugz is a great web-based project management and bug tracking application that we use to keep track of our customer's projects.  I'm often suprised by the quality and modern feel of this app, despite running in classic ASP*.  So I was pleasantly suprised again when I found they'd come out with an API and Visual Studio 2005 Plugin.  Installation was simple, and the result is a very Team System-ey integration between our helpdesk and development environment. 

*As a side note, it's actually written in a proprietary language, Wasabi, which has driven some to (perhaps rightly) question the owner.