This is a Mecanum wheel
http://en.wikipedia.org/wiki/Mecanum_wheel
I saw that somebody else had a printable one, but it was not shared. So I made this.

You will have to use glue, or acetone, or something to accach the pieces together.

This is designed to use 3mm filament as axles for the wheels.

I also uploaded the blender file, in case anyone wants to change stuff.

Print all the bits out. Either individually or in the sets I made.
Attach the wheel holders to the hub. Make sure to get them all lined up properly.
Add the wheels using 3mm filament.
Make a sweet robot. :)