Merchant Accounts allow you to accept credit cards. A Merchant Account is considered to be vital in the business world today, particularly for people selling over the web.
If you are looking for good merchant accounts, then I reccomend the Top Merchant Accounts site. It will not be long before you can be accepting MasterCard, Visa, and Amex.
(merchant accounts give your business instant credibility, and dramatically increase sales!).
There are of course other ways to increase the profitability of your web site. The best of these is by increasing your product range using associate programs and affiliate programs.
But don't forget that there is no substitute for good Merchant Accounts!