How can I "redeem" a private key without downloading a client? Let's say that I have generated some private keys offline and use them for my savings. For my spending money I prefer to use an online wallet instead of downloading the client.

Is there any service online where I can enter


My private key
A destination address (the online wallet)


and simply click a button to send the whole balance to the destination address?
It [edit: was] possible to redeem a private key at MtGox. Under "Add funds", choose "Redeem private key" and pick the format that you want to enter the private key in. The full amount of the private key will be added to your MtGox account.

Update: It is also possible at My Wallet (blockchain.info).

Update2: Mycelium wallet for Android app has a "cold storage" feature.  You simply scan (or enter) the private key, then scan (or enter) the Bitcoin address t send the funds to.  Hit send and you are done.