Second-Stage Small Business Development Act of 2006 - Directs the Administrator of the Small Business Administration (SBA) to carry out a four-year pilot program to make grants to eligible entities for the development of peer learning opportunities for second-stage small businesses. Defines a "second-stage small business concern" as one that: (1) has experienced high growth in specified demonstrable ways; and (2) does not exceed the size standard for the North American Industrial Classification System code of such concern. Provides a minimum grant amount of $50,000.