Alternative to Groove?

jpmahala writes: We had been using Groove internally at our company for quite some time (before the Microsoft buyout), and were interested in adding more users to the program. However, after clicking on the link to the store on Groove's website, I find a message from Microsoft that the product is no longer being offered. Following the link provided by Microsoft , I find that it is bundled into the Office2007 product now and it does not seem to be offered as a standalone product.

I'm sad to see that sort of thing happen, and I am unwilling to upgrade everyone to Office2007 just for the sake of Groove. Is there any viable alternative out there?