[QUOTE=How does one remove a nut that has been stripped with a crescent wrench?
[/QUOTE]
TIG weld the wrench to the nut first, then it will work.
Seriously though, they have several wrenches at Sears, K-mart and Walmart along with most auto parts stores that clamp down harder on the nut the more you put pressure on the wrench.
They look like these :
Grip Wrench The ones I bought are solid though.