Incarnates are fantastic at boosting skill checks, and the social skills are no exception. They don't have any in-class uses for Charisma, but to be honest, they don't need it. (Alternatively, you could go into Incandescent Champion after you get the levels of binds that you're happy with... IC is usually a pretty bad prestige class, but you don't lose your Incarnate abilities, and you get a use for Charisma.)

Warlocks use Charisma and get an invocation that gives them +6 to (I believe) Bluff, Diplomacy, and Intimidate.