Register with Bitstamp, provide paperwork (passport + U.S. drivers license is probably best bet), wait a few days for them to process, sell Bitcoins, wire transfer to your U.S. bank account, wait ~ 5 days to clear, profit!
Once you've done this once, everything will go a lot faster next time.
Don't bother with mtgox, there's a reason why there's such a price discrepancy and we all use Bitstamp as the real exchange rate.
EDIT: I just read elsewhere that mtgox is still highly liquid if you're in Japan or China, which means that there may be a good reason for the price discrepancy (high demand in China). But don't bother with gox if you're in the U.S.
Once you've done this once, everything will go a lot faster next time.
Don't bother with mtgox, there's a reason why there's such a price discrepancy and we all use Bitstamp as the real exchange rate.
EDIT: I just read elsewhere that mtgox is still highly liquid if you're in Japan or China, which means that there may be a good reason for the price discrepancy (high demand in China). But don't bother with gox if you're in the U.S.