Our friends at the Heritage Foundation have created an invaluable online tool for learning about the U.S. Constitution:

The Heritage Guide to the Constitution is intended to provide a brief and accurate explanation of each clause of the Constitution as envisioned by the Framers and as applied in contemporary law. Its particular aim is to provide lawmakers with a means to defend their role and to fulfill their responsibilities in our constitutional order. Yet while the Guide will provide a reliable reference for lawmakers and policy-makers, and be especially useful for the trained jurist, it is written to be explanatory and educational, accessible and helpful for informed citizens and students of the Constitution generally.

Check it out here.