Imagine iChat, Messages or IRC merged with your favorite to-do system like Things, Clear or Taskpaper. You get Kickoff. Now available in a public beta, this OS X Mountain Lion app helps groups coordinate and plan together. It's superficially similar to the 37 Signals web chat tool Campfire, but in convenient app form.
The app offers strong team features including separate message threads for tasks, a main chat "room" and easy file sharing. Just drag a file into the chat and it easily replaces email distribution.
Even better, the conversations and chat threads are preserved when you leave, so you can scroll back and pick up where you left off, catching up with whatever tasks, discussions and updates have been covered.
I do worry, a little, that among chatty teams (and trust me, the TUAW team is full of chat), the amount of back and forth may distract from catching key info. Being able to move important matters from the primary discussion to actual to-do tasks helps mitigate that worry.
Overall, I was very impressed with my initial testing. I think Kickoff is definitely a product to keep an eye on.
Here's the Kickoff promotional video.