How can I export the private key for an address from the satoshi client? If I want to transfer an address from the satoshi client into a different client, how can I find its private key to do so?
To export a private key from your Satoshi bitcoin-qt client:


launch your bitcoin client as usual and wait for it to load the blockchain and start up
click on 'help' in the menu bar (top right) 
click on 'debug window' 
select the 'console' tab
type: walletpassphrase "your walletpassphrase here" 600
type: dumpprivkey [your Bitcoin address here] 
this will return the private key, you can copy it now; ensure you clear your clipboard/history afterwards
type: walletlock