Microway, a systems integration specialized focusing on high-end GPGPU systems, has published a PDF slide deck showing the various capabilities and specifications on the higher end NVidia and ATI video cards. It includes details on memory structures, silicon design, core counts, and much more in easy tabulated forms.
Read the whitepaper here (Online with Google Viewer) and check out their website.
Randall Hand
Randall Hand is a computer graphics programmer and news junky that's been working in the field for the last 15 years. He's responsible for visualizations generated on some of the most powerful supercomputers in the world, ytnef, mullion support in ParaView, and VizWorld.com.