From Wikipedia:
Echo — The main character. A Doll who begins, in her mind-wiped state, to become self-aware.
Adelle DeWitt — Beautiful, sophisticated, cold as an alp. Runs the Dollhouse with an efficiency that is both ruthless and protective. Would die before she showed anyone how lonely she is.
Paul Smith (or Paul Ballard)[19] — An FBI field agent, he's been chasing the urban myth of the "Dollhouse" long enough to have lost any shot at promotion. Becomes obsessed with, and twisted romantic foil for, Echo.
Topher Brink - Genius programmer who's articulate, nerdily attractive, and blithely amoral. He's responsible for imprinting the dolls — and making sure they stay unaware of anything. Is fascinated by the science and kind of digging the illegality. Fun to be around, but might not be remotely trustworthy.
Sierra - A Doll like Echo, she has every personality in the world but her own. Is not as self-aware as Echo, but is instinctively drawn to her as a friend.
Victor - A Doll, and the other closest thing to a friend Echo has. Childlike when he's inactive, and everything from Errol Flynn to (young) DeNiro when he's active.
Boyd Langton - An ex-cop, Boyd is Echo's 'handler' - her guard/bodyguard. Hates himself for taking this job, but he'd lay down his life to protect the people he feels he's exploiting.
