Btcoin Fog is a proven gold standard when it comes to taknig your privacy seriously. The downside is Bitcoin Fog does require six confirmations for deposits and will set a minimum delay of six hours for withdrawals at random times during the process. This is a sound process for those approaching their transactions in a structured and planned manner. It is not ideal for anyone trying to get money quickly from one account to another. The fees are fully random and will range between 1-3% of your deposit.
Update: As of February 1, 2017 BitcoinFog appears to have closed and shut its doors. We recommend now using Helix Grams instead.