or simply import the privatekey into your client and 'bam' the public address appears.
It's easy to get the public key, but actually importing the private key into a client has been a nightmare for me. I tried to do this on ALL the Android bitcoin apps, plus Electrum, and they all refused for different reasons. I tried Multibit but it took forever to download the blockchain. Finally I just used blockchain.info as I nervously sent the funds from a paper wallet that I realized may be insecure to a new, more secure one. This experience made me realize how far we are from mainstream adoption (joe blow really has to use paper savings wallets for large amounts, yet something as simple as redeeming a private key is incredibly difficult).
