Quote from: RealT on November 08, 2013, 01:32:45 PM

In the scenario of importing the private key into an online wallet for the purposes of sending funds to another person what is an example of a good online wallet for this purpose?

Some examples:

Bitcoin-Qt
Armory
Electrum
MultiBit

Quote from: RealT on November 08, 2013, 01:32:45 PM

Can portions of funds be imported from an address or does the entire portion have to be imported?
Thanks

Funds aren't stored in addresses. Funds are stored in the public blockchain that every full node as a complete copy of. Therefore, you don't "import funds" partially or otherwise.

Private keys allow you to sign transactions that update the blockchain. A wallet chooses unspent outputs from the blockchain, spends them in the "input" side of the transaction providing value to the transaction, then creates new unspent outputs in the "output" side of the transaction to assign that value elsewhere. Each unspent output used as an input requires a digital signature. The digital signature requires the use of the private key that is associated with the address that the unspent output was previously assigned to. The wallet uses the private keys that it has control over to provide these digital signatures in the transactions that it creates.

You import a private key into a wallet. The wallet uses the private key and calculates the bitcoin address that is associated with the private key. The wallet then scans the entire list of unspent outputs that the wallet has obtained from the blockchain, and searches for every unspent output that is associate with that address. The wallet then displays a number that indicates to you the total of the unspent outputs so that you know how much value the wallet can control with the private key.

You can spend some of the unspent outputs or you can spend all of them. Regardless, once you import the private key into a wallet on a computer you should dispose of the "paper wallet". If there are any funds left in the wallet on the computer when you are done with your transactions, and if you want to return those funds to a "paper wallet", you can create a new "paper wallet" and create a transaction to assign the remaining unspent outputs controlled by that imported private key to the new paper wallet.