This Nation
This nation.com: Executive Order 13132 of August 4, 1999
This Executive Order signed by President Bill Clinton on 8/4/99 is an order that describes the balance between state and federal governments, as warranted by the Framers of the Constitution and federalism.
University of Groningen
American History: Outlines: The Legislative Branch: The Reach of Congress
This well-written and well-organized site from The Legislative Branch provides a thorough overview of congressional powers, inherent checks and balances, as well as links to related information.