What methods are available to accept Bitcoin payments?
There are a number of approaches, and the best method for you will vary on a number of factors.

For instance, if you sell a digital good it might be easier to simply sell the item through an online store like CoinDL, where you simply direct your customers there.

Similarly, if you sell a couple of items at a fixed rate, you could sell it on BitMit.net, again -- your e-commerce site simply directs your site visitors looking to pay with bitcoins there.  A blog post on Coinbase describes a "Buy Now" button modeled after another leading e-commerce payment solution.

If you already use an e-commerce shopping cart you might have an easy way to start accepting bitcoin if there is a module for that cart interface software that accepts bitcoin. 

When following the DIY route, you can have the proceeds of your sales converted to fiat upon receipt.  Some exchanges (like Mt. Gox) offer "autosell" for shopping cart tools so that proceeds convert to USDs (or other currency) upon receipt. 

The easiest way, however, is to use a payment processor like BitPay, WalletBit, Paysius, and ZipBit.  These are used in a similar way that a site uses PayPal to accept payment online.  The payment processor will provide all that is needed for your e-commerce site, and will provide a method to receive cash via a bank transfer.