If you're looking for a powerfull (but easy to use) collaboration tool for your web project, I advice you ActiveCollab. I use it with teams around the world to centralize discussions and feedbacks. It's really a good tool.

With ActiveCollab you can manage time, files, discussions, tickets and documentation. A newsfeed allow you to know what is new on your projects. If you're an iPhone addict, there's also an webapp for that :-)

More : http://www.activecollab.com