Some of the hard specs on Nvidia's completely next-gen Fermi graphics cards have been out there, but this is what you can actually buy around April 12: The $500 GeForce GTX 480 and $350 GeForce GTX 470.
Nvidia's calling the GTX 480 the "fastest video card in the world" with 480 processing cores (ha) and 1.5GB of video RAM. It eats up 250W of power, so stringing together 2 or 3 via SLI would require a small power plant in your PC. Slightly less ridiculous is the GTX 470, with 448 cores, 1.28GB of RAM and pulling 215W, for $350. Nvidia's benchmarks obviously show it crushing some of ATI's top-of-the-line 5000 series cards, but we'll leave the hardcore benchmarking to our nerdier friends out there (which should be coming shortly).
Nvidia's promising "tens of thousands" of the cards will be available at launch, and you should start seeing them sometime around April 12, though you might find 'em earlier. [Nvidia]