Interact with the "Outgoing" Address Book via RPC?

[twmz]

Is it possible to interact with the address book of external addresses via the JSON-RPC API?  For example, for a given transaction or address find out what the user-friendly label is for that destination address?  Or to assign a new user-friendly label for an address prior to, or while sending bitcoins?

If this has been asked before, please feel free to point me at the answer.  I failed to find anything via a brief search.