2 words:
French Laundry
Ok, several more words.
Best restaurant in the state. Possibly the country. its in yountville.
Thomas Keller also has another restaurant called bouchon. you might end up checking this out if you can't get reservations at french laundry.
http://en.wikipedia.org/wiki/French_Laundry
http://www.frenchlaundry.com/bouchon/bouchon.htm