I finally figured out how to do Ubergrinds, for all of you SSX Blur fans that don't know how to. Well, I've only figured out the handstand one but I'm sure it isn't hard to figure out the rest.
For the handstand Ubergrind, just draw the "Z" while on a rail. Draw it just like you would in the air (press A, draw Z, let go of A).
Does anyone know how to do the other Ubergrinds?