listreceivedbyaddress [minconf=1] [includeempty=false]
[minconf] is the minimum number of confirmations before payments are included.
[includeempty] whether to include addresses that haven't received any payments.
Returns an array of objects containing:
"address" : receiving address
"label" : the label of the receiving address
"amount" : total amount received by the address
"confirmations" : number of confirmations of the most recent transaction included
or listreceivedbylabel if you're labelling addresses with their username.
So far I've concentrated on functions for web merchants, not so much on stuff for remote management of headless coin generators yet.