Interesting resource lists all state level pending legislation, and new laws, for debit and credit cards. 64 bills in 27 states have been introduced or are pending in the 2013 legislative session. Out of the total 64 bills, 44 address credit or debit card surcharges. This reconciles state laws with changes in card acceptance rules imposed by Visa, MasterCard etc.
Update 10/13/2016: Eleven states—California, Colorado, Connecticut, Florida, Kansas, Maine, Massachusetts, New York, Oklahoma and Texas—and Puerto Rico have laws that prohibit merchants from charging consumers with surcharges on credit card transactions. Minnesota prohibits a seller of goods or services that establishes and is responsible for its own customer credit card from imposing a surcharge on a purchaser who elects to use that credit card in lieu of payment by cash, check, or similar means.
Update May 2017: Despite US Supreme Court case and judgement, surcharging is still illegal in NYS.