Not a big wine drinker? You can still enjoy Napa with an artisanal olive oil themed trip!

Closer to the Bay Area is Olive Crush in San Carlos, which does olive oil and vinegar tastings, too:

http://theolivecrush.com/

Olive Crush has the rare "5 stars out of 5" average on Yelp:

http://www.yelp.com/biz/the-olive-crush-san-carlos