From 37signals. Basecamp is a unique project collaboration tool. Projects don't fail from a lack of charts, graphs, or reports, they fail from a lack of communication and collaboration. Basecamp makes it simple to communicate and collaborate on projects. The Basecamp API is implemented as vanilla XML over HTTP.
Click the "Track this API" button on any profile page and never miss an API update, new app, or breaking news for that API again.
There are no source code libraries or how-to links for Basecamp. If you know one why not add it?
It may be good for communication, but for managing my projects I chose Wrike http://www.wrike.com/ after reading this article http://www.pcworld.com/businesscenter/article/134816/project_management_lite_basecamp_and_wrike.html
I love it. We use it daily to manage the development of our software. Go 37signals!