My current favorites are:
L'Artisan du Chocolate, on First, east of Virgil, which makes wonderful and innovative chocolates. Valerie Chocolates, as mentioned above, is right next door (I wasn't aware they had a Silverlake shop as well) and do very nice caramels.
BonBon Bar makes fabulous chocolate bars, available on-line or at selected farmers markets.
Boule had great chocolates, but is gone.