VR-Zone has posted an article on voltage modding the new GeForce 7800 GTX 512MB card.
The NVIDIA 512MB 7800 GTX is an awesome performer, with great overclocking potential. As it is, the cards produce quite an amount of heat so if you do plan on doing some voltage modding to enhance overclocking, make sure you have aided cooling.
Check it out over here. They also report about a new record of 13396 3DMarks in 3DMark05 with a highly overclocked NVIDIA GeForce 7800 GTX 512MB running at 810MHz core and 1998MHz memory. Of course this wasn't done on air but with an extreme cooling solution.