A Merchant account is a type of bank account that allows businesses to accept payments by debit or credit cards. A Merchant account is established under an agreement between an acceptor and a merchant acquiring bank for the settlement of credit card and/or debit card transactions. In some cases, a payment processor or independent sales organization is also a party to the merchant agreement. Whether a merchant enters into a merchant agreement directly with an acquiring bank, or through an aggregator such as PayPal, the agreement binds the merchant to obey the Operating Regulations established by the card brands. Source http://en.wikipedia.org/wiki/Merchant_account
If you need to establish a Merchant account or if you need to save money on your current Merchant account, go to FeeFighters.com and have Merchant account vendors compete for your business.
You can also check out Stripe which is a merchant account and a payment gateway.