Socket F is the new socket for Opteron 2xx and 8xx parts. It will have 1207 pins (as compared to the current Socket 940 with 940 pins).
Some pictures of this socket are available at tweakers.net/nieuws/39753
The AMD roadmap indicates the new socket will be released at the same time as Socket AM2
There is very little information on what those extra 407 pins will do. They will certainly allow the use of DDR2 ram in speeds of 400, 533 and 667 MHz and possibly 800Mhz (AMD recently announced that Socket AM2 would support DDR2 @ 800MHz).
About the only other thing we know about Socket F is that it will be the socket used for the upcoming quad core processors.
There are rumours that some of those extra pins may allow integration on the core of a PCI Express controller.