The GeForce 8800GTS was originally planned to be launched earlier this month, but had its launch delayed by Nvidia. At first they did not mention why, nor when they would officially release the card. Now they have committed to a new release date, saying the units will be available in the second week of December on the 11th. The card has been eagerly anticipated, and the delay, while slight, might indicate that Nvidia is expecting huge demand or is having difficulty meeting their supply quota.
In either case, the short delay will probably not affect retail availability, at least not so much that Nvidia cared to announce.