Marcopolini: Campbell-based Marcopolini imports high-quality, hand-made leather goods from Italy, including iPhone cases. I own a Marcopolini key wallet (which, for those who don’t know, is a keychain that stows your keys inside a coin-purse-like wallet, so your keys don’t punch holes in your pockets). It is extremely well made, and its leather keeps looking better as it ages.
Chrome: When I lived in the real Bay Area (i.e., the Bay Area in which you can see the Golden Gate and/or Bay Bridge with minimal effort), Chrome was the most ubiquitous brand of messenger bags and backpacks. Now, they've expanded their line to include everything a bike-messenger-type urbanite needs for day-to-day living, including a way-overbuilt (but probably quite useful) iPhone case/handheld-radio case/all-things-small-carrying case that they call the Pro Series Access Pouch.
Jaqet: Los Angeles-based Jaqet makes minimalist, clean-lined handmade-in-California leather goods, including iPhone cases.
DODOcase: San Francisco-based DODOcase makes muted, well-constructed-looking (I've never seen one myself, but they look nice on the website), functional things in which to put other things, including iPhone cases.