Basecamp

If you have a need for project management and hate Microsoft Project, Basecamp may be the answer for you. It is a web-based collaboration tool focusing on communication through messages and comments. Of course, Basecamp also offers organizational tools such as milestones, to-dos, file uploads (with versioning), and a simple wiki they call Writeboards. Notifications occur through emails, so you don't have to constantly check the website.

I've been using it successfully for over 5 months now. The beauty of Basecamp lies in its simplicity. Designers, software developers, system administrators, and clients alike have found it intuitive and useful.

To satisfy your inner geek, Basecamp offers RSS feeds for your pojects and an API to build upon their core functionality. I wish I built this tool. More importantly, I wish I had their 1,000,000 users.