First, thanks to the board for all the great information - just back from Barcelona & wouldn't have eaten nearly as well without it.
The two spots I have to add to the general wealth of posts are an organic bread store: Barcelonareykjavik on Doctor Dou (excellent stop if you are at the Boqueria), and a Gingers, on C. Sant Just (Barri Gotic). Gingers serves wine & a small menu of small plates - they have a good cook. It's a fine spot to eat alone / read a book, too.
We managed to get to:
El Quim & Bar Pinocchio in la Boqueria, Pollo Rico, Paco Meralgo (Twice. It serves more for lunch than for dinner), Txakolin (we had an excellent & inexpensive lunch downstairs), La Paradeta (yum!), Senyor Parellada. (Great service & inexpensive for dinner, but I wasn't crazy about the things we ate), Caelum for the "blessed" hot chocolate.
Also on the recommendation of someone on this board, I took the one-day cooking class with Catacurian (http://www.catacurian.com/). It was a treat.