The ones I post on or read regularly:
Dog.com, Stableminds, Just Labradors, Lab Breeders, Wiscoy, the UKC Forums, a couple of small forums that were made when the Acme boards died, Paintball Nation and Dog Chat. There's a Lab board that went from a message board to an email list, and now FB, and there's bunch of other boards that I signed up for but never even look at anymore.