Blockchain.info's wallet can be accessed via tor by their following onion address mentioned here: https://blockchain.info/wallet/anonymity
But this is generally not a good idea since you will be dealing with your own money and an exit node can easily intercept your username/wallet identifier.

According to the anonymity, you can use Bitmixer.io if you want our coins to be untraceable from a particular address. The more frequently you mix the coins, more difficult it becomes to trace it.