Since I am working on several collaboritve project with people from around the world, I have been using the Groove and Sharepoint as shared work spaces. eRoom is not a good choice becasue it is much to expensive for personal use, but Groove, and Sharepoint can be used effectivelly. Groove has much more functionality and, when the replication works well, it is very easy to exchange documents with other team members. One difficulty that we hare having, however, is that a number of my colleagues use Macs, not PCs, so they have to run Groove in Virtual PC. I don't think we have gotten it to work properly yet, but we are working on it. I think Groove has a Mac client coming out soon.
Microsoft Sharepoint is entirely web based which eliminates many of the problems of connectivity that we have been having. My colleagues with Macs can get in, although bCentral says the Mac OS 10 is not supported by Sharepiont or bCentral. What big problems! I have searched for other cross platform collaboration environments but I have not been able to find a suitable one yet.
Hopefully Groove will work, as promised, with sharepoint soon, and their Mac client will come out too!