I have used Chowhound a number of times when I've gone out of town, and have found some good places that way. I've kind of felt bad that I've had little to offer in the way of recommendations, though. I live in Pittsburgh, but for whatever reason, I stick with the same couple of places, and often base my choices on who has the best craft beer selection. (Probably Blue Dust, but I digress...)
But it occurs to me I do know bakeries, at least to some extent. So for what it's worth, a couple of unsolicited opinions on local bakeries:
Pastries a la Carte, Pleasant Hills - I know they're not a big secret, to judge from the crowds in this tiny shop, but they are head and shoulders above anywhere else, I believe. Their cakes are very good, and made beautifully. (Recently I saw them boxing a layer cake made to look like a cup of hot chocolate with bubbles overflowing. Very cool.)
But it's their cookies that make it worth the trip, from almost anywhere. I have never had bakery cookies that taste so close to homemade - or actually, better than almost any homemade cookies I've tried. Try the Allie cream sandwiches (I believe they're called): small, delicious wafer cookies with an ethereal cream inside. Their refrigerated goodies, like small mousses and big napoleons, are also wonderful.
It's a dreary trip on Route 51 to get there, and if you're not careful you'll miss it, but it's the best.
Eadie's, US Steel Building, downtown - A popular to-go stop for downtown workers. Their other offerings are OK, the place is a little dumpy - but they have perhaps the best cakes in town. I usually insist on an Eadie's cake for my birthday, if my husband's willing to go downtown and find a place to park. Moist cake, icing that doesn't taste like it was made in a lab - and the cake doesn't harden and get yucky the next day.
Prantl's, Shadyside - The favorite bakery of lots of Pittsburgh natives. Does anyone else remember the bread shaped as a turtle, with a sign stuck on it saying "I'll hold the hors d'oeuvres"? For YEARS they had that in the window.
Best thing to get at Prantl's. by a mile, is the burnt almond torte. Other places attempt it, but if theirs isn't the original, it's probably still the best. I had a priest (A PRIEST) tell me, as he ate a piece: "This is why God became man."
A plate of their mini-cakes and tassies is a lovely dinner-party dessert. And their cakes are also awesome, ranking behind Eadie's by maybe a hair. They charge based on their reputation, though.
Potomac Bakery, Dormont and Mt. Lebanon - Good bread, excellent brownies with yummy chocolate icing, decent cookies, very good doughnuts, and cakes that rank up there with the best.
Giant Eagle, everywhere - You know what, in a pinch, their cakes aren't bad at all. I used to love the giant chocolate-chip cookies, but they just taste so artificial to me now - don't know whether it's me or them. I have to say though: every time I leave there without a box of chocolate mini-gobs is a moral triumph. Not easy.
I know there's Chatellier's in Millvale - kind of out of my way, haven't been there since it flooded, but I need to go back. I'm sure there are other places I've missed as well. But those are my favorites, in any case.