A recent thread queried hounds on where to find Plugrá, a slow-churned European-style butter that has a higher butterfat content and less water than typical American butters, resulting in better flavor and texture for baked goods. Trader Joe's stopped carrying the one-pound butter brick that proves a much better value than the half-pound size more commonly found in stores. Oasis Food Market in Oakland carries the one-pound size, and Whole Foods on Fourth Street in San Francisco sells the one-pounder.
For locally made butters, suggestions included McClelland's and Straus. Your editor puts in a vote for Vella's lightly salted butter, which is sold at Bi-Rite and was also recommended in this thread from 2005.
Whole Foods Market [SOMA]
399 Fourth Street, San Francisco
Bi-Rite Market [Mission District]
3639 18th Street, San Francisco