LittleBigPlanet’s getting its long-awaited Online Create mode next week, which’ll allow you and your sack-buddies to put levels together over PSN. See here.
Up to four players will be able to contribute to levels at once. This is part of the 1.21 Leerdammer update, which also includes location-based matchmaking and tons of other additions and fixes.
Check out the official Media Molecule/LBP site for a video on the new features.