We were in Napa last week, so there will be more to follow
We did a Bordeaux blending seminar at Conn Creek--this is ranked as one of the best Napa experiences--and it was.
They have 14 Cabernet Sauvignon barrels from all over the Napa Valley for you to taste (as much as you want) for about half an hour. You can mix them, too, to see how they go together. They have one barrel each of the other 4 Bordeaux varietals-Merlot, Malbec, Cab Franc, Petit Verdot.
Then you make a mixture of whatever you want. If you're happy, you then create a bottle with the same proportions, cork it, make a label and take it home.
$90 per person, $65 if you join their club for a year--but you go home with a bottle worth $50-70.
Link below picture