A month or two ago I was toying with making a Katamari Damacy clone and produced a little demo, "Catamary".

It's not much and I haven't had time to work on it since but for those needing badly to roll over something here it is: http://clydeshaffer.com/clydeshaffer/downloadables/catamary.rar
The controls are WASD and IJKL to imitate the double-directional controls from the playstation. Also if you press spacebar the ball pulls a complete 180 degree (or 2 * pi radian :D) turn.

Wonderful End Of The World?
Nice game, but the ball is too slow.

Well, Wonderful End of the World is neat but I missed the rolling from Katamari

I might work on this some more later, but I've gotta fine-tune the processes of attaching things to the ball correctly and my formula for determining whether you're big enough to pick up a particular object, before I get concerned with fine-tuning simple variable changes such as movement speed.

Rather than simulating every single object attached, I'm using an invisible spherical hitbox so I also gotta work on how I alter the size of the ball for each object added.