Napa and Sonoma are fine for a weekend trip -- if you enjoy ridiculous crowds and buses full of tourists. But in the same time it takes you to get to Napa (be honest -- it’s two hours with traffic), you can instead get to Mendocino County: a 4,000-square-mile beer-drinkers paradise (THAT HAS AWESOME WINE TOO).
There's no way you're gonna be able to see it all in one weekend, but the trip from Hopland to Anderson Valley to Fort Bragg and then back is totally doable, AND gives you a chance to eat and drink while surrounded by small towns, epic vineyards, towering redwoods (keep an eye out for Ewoks!), and the majestic North Coast. Oh, and in parts of Mendocino they have their own language (it's called Boontling), so don't be weirded out when someone asks if you want some fratty, horn, and gorms (that's wine, drink, and food). Bahl hornin', bro! (Cheers, bro!)