This report from the National Conference of State Legislatures discusses the federal mandate for states to establish health insurance exchanges. It explores the options that states have when creating these and looks at the status of individuals states in the implementation process.

From the report: 

The 2010 Affordable Care Act (ACA) requires state-based American Benefit Exchanges to be established and working by 2014. The ACA gives states the option to establish one or more state or regional exchange, or to merge with other state exchanges. If a state chooses not to create an exchange, the federal government will set up the exchange(s) in the state.

States are at different starting points for establishing exchanges. A couple  already have exchanges (Massachusetts and Utah), and California has recently passed legislation to establish one. Some states are studying and evaluating how exchanges work, while others are identifying who to involve in the discussion about creating an exchange. And others are identifying existing structures, such as state employee or small business exchanges that could serve as a starting point for planning. 

Exchanges are, for most states, new entities that will function as a marketplace for buyers of health insurance, giving them choices for health coverage. They will offer a variety of certified health plans and provide information and educational services to help consumers understand their options. The initial target customers for an exchange will be people who purchase coverage on their own and small businesses with up to 100 employees. In the future, exchanges may be expanded to larger employers. 

Full Report: State Actions to Implement the American Health Benefit Exchange

National Conference of State Legislatures. (2010). State actions to implement the American Health Benefit Exchange.