I've been using Basecamp for freelance consulting and I absolutely love it. I have one problem with it, once you shut down a project the client can't get any of their materials. It would be nice if you could export the entire contents of a project, compile it into a .pdf, and ship it off to a client as part of a project closeout.
They have a pretty thorough API, and I happen to know a language that can make pdf's pretty easy. So I figured I could make my own solution, and I did. In doing so, I had to create a service CFC for the Basecamp API. Since there wasn't one when I looked around for it, but there were a few questions about one, I figured I would share it on RIAForge, and I have. You can download BasecampCFC from there now.
At the download page, Terrence also says, "Not all of the Basecamp API items are implemented. If you want a Basecamp API method implemented, please drop me a line and I will get it working." (His "About" page includes his contact info.) Thanks Terrence!