Of all the web application out there to manage projects, this is one of the best I have seen.  I have been using it for a few years, and not just testing it.

Here are a few things that I like:

– Very nice interface

– good iPhone and Android app

– constant and regular improvements.  There are really working hard on the app to make it better

– integration with many others service, such as Dropbox, Box.net (starting at the Enterprise 2 level of account)

– Nice set of options, including time management, file management, notebooks, risk management.

many other features that you can find here.

There offer a free account for up to 2 active projects.

If you are looking for a web application for project management and team collaboration, it is definitely one to consider.