1.0) Using Coinbase, (coinbase dot com) is currently my preferred way. Create an account there and do your homework. They have made the process rather straight forward once you are verified.
1.1) The fastest way to get verified is to link your US based bank account to their service. I would suggest buying a small fraction of one BTC to get verified more quickly, rather than having Coinbase send a couple transactions to your US bank account for you to verify.
1.2) Answer the Coinbase security verification questionnaire quickly. They are following the Know Your Client (KYC) rules. If you take long to answer the questions your verification will fail and you will need to wait 24 hours to try again. In this context KYC refers to due diligence activities that financial institutions and other regulated companies must perform to ascertain relevant information from their clients for the purpose of doing business with them in the USA.
2) Convert your USD at MtGox to BTC and send it to your account at Coinbase.
3) After you have been verified you can convert your BTC to USD and transfer the USD into your US bank account rather quickly.
Note that the price you are selling the BTC at Coinbase is less then what you paid for them at MtGox which can be $ignificant if you have many BTC to sell for USD. There are other ways but this is one that has been working well for me. . .