Tom Woods gave a great speech to NullifyNow NC recently that is great for those who already have a grasp on the concept of state nullification:
Tom Woods NullifyNow NC
In this speech, Woods focuses on combating the popular notion that the US is simply "one giant blob" (his words) by giving historical examples which show that the opposite is true- that the US was simply a "collection of societies" which agreed to a compact. This culminated in the founding of a limited federal government by the states, and provides credence to the philosophy that when the federal government steps outside of the powers granted to it, the states have the duty and the right to interpose on behalf of their constituents.
This concept, although conceived and popularized long ago, has obvious contemporary relevancy, and is currently being used in many states to combat federal laws that constituents find reproachable. Examples can be found in state-level opposition to national health care, gun laws, and marijuana laws- all issues which are either expressly or implicitly outside the purview of the federal government. Nullifying federal laws is a bold step to take, and states who do so should be applauded for having the courage to stand between the federal government and the constituents they represent.