Resistor Cube

Two posts in one month? Crazy. Anyway, I got a new puzzle, which I learned from the electromagnetism course I was teaching this term....well, sort of, I expanded a simpler puzzle into a surprisingly awesome one.

Consider a cube, whose edges are 1 Ohm resistors, what is the effective resistance between opposite corners of the cube?

Sad that its really a physics puzzle, I prefer doing more math when I can, but I'm not sure how to turn this puzzle into a fully mathematical one. Anyway, the real puzzle is to generalize that puzzle into N dimensions. So, have fun with that.