You can also use something like blockchain.info for slightly better security than coinbase. They do client-side encryption and decryption of wallets. Of course,

You can also use something like blockchain.info for slightly better security than coinbase. They do client-side encryption and decryption of wallets. Of course, if you forget your password, your coins are gone. And blockchain.info could always modify their code to steal your coins later. At least they couldn't steal them without you logging in. But a thin wallet like Electrum is probably your best bet.