222Doc, co-author of Building Robots with LEGO Mindstorms NXT, after managing his Lego robot to make his first stair step now raises the challenge by steping up 3 steps!
The mechanics of weight balancing is brilliant and even though is a bit slow the robot manages to step up with confidence.
The maker claims is the first Lego biped to achieve this and we have no reason not to believe him. You can search more info here and here.
More Lego NXT projects can be found here.