The only required components would be two NAC appliances (one Clean Access Server and Clean Access Manager), see: http://www.cisco.com/en/US/products/ps6128/products_data_sheet0900aecd802da1b5.html
Of course, having other security products in conjunction with the appliance can greatly enhance the solution (CSA, CS-MARS, etc.)
I have found that the hardest part about a NAC deployment is not configuring the equipment! It is determining the policies that are appropriate for you network. A whiteboarding session with a Cisco partner or your Cisco account team can really help hash this out.
