I’ve just been experiencing Yammer. (http://www.yammer.com/) It’s a pretty neat service, with a lot of familiar concepts. If you’ve used Twitter, you can use Yammer.
One of the very nice features is that you can create ‘groups’ and assign comments to the groups – the comments are still displayed in your ‘global timeline’ but having them all pre-filtered is rather nice.
I’m unsure how it’s going to scale to 100’s of users and 100’s of groups giving 1000’s of comments, but there’s certainly something compelling about using it as an interaction technology.
#yam becoming more prevalent in Twitter as well – augh micro-blogging time.