IBM have launched their OpenSim-based 3D meeting solution integrated with Lotus Sametime.  It is much more impressive than I had expected judging from the details and video posted here, and could be quite compelling for organisations that already have an investment in SameTime.  Of course, for anyone who doesn't, well I'd recommend Roobaab - we will be providing many of the same meeting features, and others, all tightly integrated to a unique really useful content management system.