A really lovely winery in this area is Chateau Montelena in Calistoga. Their wines were made famous when they won the Paris Tasting in 1976. (In the "blind" tasting the nine French judges awarded Montelena's 1973 Pinot Chardonnay first place.)
The 2008 delightful movie Bottle Shock was about Chateau Montelena and "the judgement of Paris". It's a fun movie and you can get a feel for the early years in the California wine country. You can click on the iTunes button to rent or buy the video.
If you visit Chateau Montelena, don't forget to walk down to Jade Lake on the estate. It's beautiful (and is accessible for those in wheel chairs).