California - Napa: Any must see wineries?

We're staying in St. Helena, CA. I don't know beans about wine. Any must sees? Specifically, excellent but little-known wineries?

A few months ago, I had business in SJC and brought my wife along. We went to the Robert Mondavi vineyard, and took their excellent vineyard tour + wine tasting package. The tour included some basics about grapes and growing, a drive through the vineyards, a tour of the mixing barrels and fermentation process, aging barrels, and bottling. They have an "exclusive" up-scale To-Kalon vineyard brand that you can only purchase there that is really quite good wine. My wife and I really enjoyed ourselves. There are a TON of small vineyards on the main road through Napa Valley, with lots of neat little cafe's to stop at and the like. You can easily make it a whole-day affair.

I agree with the Mondavi suggestion. Their tour is a great introduction to Napa wineries. The other one I really like is Sterling, for both the location and the Sauvingnon Blanc. I have not been to Napa in several years, so have to leave other recommendations to other FTers.

Clos Pegase, in Calistoga, was a favorite of mine when I visited the area. The owner and his wife are big art collectors, so there are some sculptures on the grounds and other interesting things to see. The vineyard also has a cave used for aging the wine. Of course the wine is pretty tsaty too:) Calistoga is a nice little town, worth checking out if you're in the area.

http://www.flyertalk.com/forum/showthread.php?t=302248&highlight=napa

Also think about visiting Von Strasser - for tasting, I am not sure they do tours (?)

Make sure to stop and eat lunch at Taylor's Refresher - looks like an old fast food joint, serves wine and beer, eat at picnic tables -

And the chocolatier in St. Helena is truly world class.

I always liked Sterling Vineyards, not necessarily for their wines, but because of the neat tram ride to the top of the hill where the winery is located. They have a self-guided tour which is rather nice. It's a beautiful location.

Chateau Montelena is well-known (for good reason!), but a beautiful winery & grounds to visit.