http://blockexplorer.com/Armory
And there are a few others, I believe.
I also have a little AHK script (which auto-refreshes the address balance from blockchain.info)
that I made for my own use (Windows only.) I will consider cleaning it up and releasing it.
Does Armory allow tracking of Paper Wallets already printed?
Yes. It requires tons of RAM and local storage of the blockchain, though.
Another option that comes to mind is Electrum - with a little tweak, you can track a public address without importing its private key.