A couple of weeks ago we were lucky enough to get a sneak preview of the Web Lab that Tellart have built for Google and the Science Museum. (I think Matt wanted to see some actual kids playing with it, and he was just being nice.)
It wasn't all working when we were there, but the interactive music stuff was - and it's absolutely fantastic. Well worth a visit. They've managed to bring off the feat of building an interactive thing, that has people playing real instruments in the room and people playing real instruments via the web - together - and getting it to sound good, coherent, satisfying and musical. It's pretty impressive. Especially when you consider the challenges of getting video and instruments to sync between the web and the world.
You might remember the lovely Valentine's project they made - playing songs on their little bells via the internet. It's like that, but an orchestra of it.
The whole thing is magnificently made; the opposite of thrown together. Beautifully shaped and painted steel, well considered details. You want to stroke and lick it all. You should go and play.