We had planned on covering at least three wineries, but after visiting ZD for their Library Wine Tasting, we only managed one that day. At $20 dollars per person (refunded if you purchase some wine after the tasting), it might "seem" like a pricier tasting. However, the four of us figured that we must have had at least a bottle of wine each by the time we were done--including tastings direct from both barrels and stainless steel vats (note, we're not professional tasters and are not capable of spitting out good wine. We just drink lots and lots of water). Our guide for the tour was very nice and knowledgeable, as well as accommodating.
Be sure to make a reservation for the Library Tour (800-487-7757). They also host wine & cheese tasting seminars.
For more on ZD, visit their site at http://www.zdwines.com. ZD was started by Norman de Leuze and Gino Zepponi (former aerospace engineers) in 1969, so the winery is actually one of the elder statesmen (in a way).
I highly recommend their Pinot Noir and Cab, though they are perhaps better known for their Chardonay.