Maybe you've already seen it, but a friend just sent me this video for a LittleBigPlanet-style physics game/toy called Phun. I'll have to try it out later because it looks pretty cool. Why not ease the wait till fall a bit by playing around with this thing? I don't really know what features this has in common with LBP (I haven't seen water in any trailers, for example), but you can definitely start prototyping some crazy objects and levels.
Download the beta here: http://www.acc.umu.se/~emilk/
Download the beta here: http://www.acc.umu.se/~emilk/