From today on European PS3 users can sign in for the beta of LittleBigPlanet Karting! This isn't the first beta of LBP out there, since not so long ago we also got the great beta of: LittleBigPlanet Vita.
Beta Sign-Up [European Site]
No words on the US sign up yet but here we have a confirmation for the US.
Beta Sign-Up [US Site]