moving money without fees what's the best way to move money within your own wallet between your own accounts and/or addresses without incurring fees?


  setaccount
   
  Sets the account associated with the given address. Assigning address that is already assigned to the same account will create a new address associated with that account.


^ That is the closest I can see but the address creation part in my opinion should instead produce a help/warn message.

If I had dust sitting on an address and wanted to move it into a larger pile on my address labeled 'main address' how would I do this?
You are asking two questions which might seem to be related but are actually very different.

To move coins between addresses, you have to create a transaction and get it included in the blockchain.  Just like any other transaction, this might require you to pay a fee.  (You might be able to send the transaction without a fee, depending on the priority and/or whether your transaction finds its way to a generous miner.)

Accounts, however, exist only within the Bitcoin Core client.  They are just a bookkeeping device to group your funds.  You can move coins between accounts with the move command in the Bitcoin Core console.  This updates the client's internal records to adjust the balances of those accounts, but doesn't actually cause any coins to move between addresses, so it has no fee.