I realise this is a bit specific... but I'm noticing that we in the East Valley have some fantastic bread.
Ciabatta from Monte Carlo Deli -- it's good by itself, it's good with olive oil, it's good with butter and conserva, and it's good toasted with (Italian, of course) tuna. A loaf costs $2.75, I think, but it's a LOT of bread.
Tchorniy khleb (black bread) from Black Jack Market, Sherman Way and Bellaire, North Hollywood -- it's one of the literally hundred of small Armenian-owned markets, where you're more likely to hear Armenian or Russian than English. Their black bread has the sponginess and sourness of a really great rye bread, with an egg-washed crust that crackles in your mouth. And it's not much more than a dollar a loaf.
Babka (sweet egg bread) from Olive Marketplace, Oxnard near Whitsett, North Hollywood -- Found in the back of the store, they're smallish (seven inches), and not jammed with raisins and dried fruit like most babka, but it's hard not to eat an entire loaf at a sitting with sweet butter. And they're $1 each.
Lavash from Karabagh Meat Market, Victory near Woodman, Valley Glen -- they don't always have fresh-made (in which case you're consigned to the usual bags), but when they do, the whole store smells like flour. Get some lamb to make shashlik, and go home and wrap it up and eat it while it's still warm.
Challah from Sam's Kosher Bakery, Burbank and Whitsett, Valley Village -- go in on Thursday, because Friday before closing it's a zoo. Get the challah. You may end up getting (and paying for) two loaves, because the clientele is strictly Orthodox and two loaves are required for Shabbat, so it may not occur to them that you only want one. Light, eggy, airy, insanely good with just butter, even better the next day for French toast.
Pain de campagne, La Spaghettata, Studio City Farmers' Market at Laurel Canyon and Ventura Place, Sunday mornings -- quite possibly the world's best sandwich bread. A bit expensive -- $3 for a boule and $4 for a miche -- but well worth it.
Sheepherder's bread, Vons, Laurel Canyon and Ventura Place, Studio City -- when other Vons and Pavilions stopped baking sheepherder's bread, the patrons of the Studio City Vons mounted a campaign to bring it back. It isn't always available (Sunday mornings are your best bet) but it can be made, and it's made in-house. I've never seen it at any other Vons in SoCal since its general withdrawal. This is your bread for tuna fish sandwiches -- the kind that sometimes gets stuck behind your upper teeth. It's wonderful.
Sourdough bread, Tallyrand Restaurant, Olive Ave. south of Verdugo, Burbank. The Tallyrand is a throwback of a diner even for Burbank, a city which was dragged kicking and screaming out of the 50's. Torn vinyl booths, substantial chairs, a menu that reads like a Stouffer's catalogue (turkey dinner; chicken in various guises; chef's salad; hamburger steak with gravy), and one of the two best sourdoughs in the Valley. They'll sell it to you, though at $4 a boule it's quite expensive -- but warm it up in an oven and it's wonderful.
Sourdough bread, Wheatland Baking, Sun Valley, sold at Fish King, Glendale. On a wooden rack in the aisle next to where you get your service number is the other candidate for best sourdough bread, from Wheatland Baking in Sun Valley. It is SOUR. It goes perfectly with lobster bisque (available in the refrigerated case not two steps away) and is available in forms from baguette to bread bowl to sliced boule.
What else is out there? This certainly isn't a comprehensive or even heavily-researched list... this is "wow, I need bread, I'm at place X, and they sell bread here." My criteria were west of the 2, east of the 405, south of the 118 and north of Mulholland and Los Feliz.