Beaulieu Vineyard (commonly known as BV) is a spot you can't miss if you are driving north through Napa Valley and is probably a name you are familiar with if you do a fair amount of wine drinking/ordering. The Georges de Latour Private Reserve Cabernet Sauvignon is one of the more famous of their labels and is named after the winery's founder (from 1900).
Tasting is available daily from 10-5. $5/tasting & $25/reserve tasting (recommended). If you are not a tannin gal, you might not love the wine, but try it anyway.
I definitely suggest eating at the Rutherford Grill before or after tasting at BV.