Skip (and anyone else), you'd be interested in these books:

S. M. Stirling, [link|http://www.amazon.com/Dies-Fire-Roc-Science-Fiction/dp/0451460413/sr=1-3/qid=1165858078/ref=sr_1_3/102-1779356-8853743?ie=UTF8&s=books|"Dies The Fire"], [link|http://www.amazon.com/Protectors-War-S-M-Stirling/dp/0451460774/sr=1-4/qid=1165858078/ref=sr_1_4/102-1779356-8853743?ie=UTF8&s=books|"The Protector's War"], and [link|http://www.amazon.com/Meeting-at-Corvallis-S-M-Stirling/dp/0451461118/sr=1-2/qid=1165858078/ref=sr_1_2/102-1779356-8853743?ie=UTF8&s=books|"Meeting At Corvallis"].

Premise: everything depending on electricity or explosions (engines, guns, steam engines, etc.) stops working, and civilization collapses when all the food and energy goes away. The people who come out on top are SCA members, history professors, and the like. In Oregon, three societies develop: in Portland, the Protector starts a medieval state based on street gangs, and opposing him are two free states, one of Wiccans and the other of mercenaries.

He also wrote a [link|http://www.amazon.com/Island-Sea-Time-S-Stirling/dp/0451456750/sr=1-7/qid=1165858078/ref=sr_1_7/102-1779356-8853743?ie=UTF8&s=books|series ]based on the premise that Nantucket gets sent back to the year 1300 BC, complete with guns, motors, airships, and the like. Basically the opposite premise of the other series. The Nantucket series came first, and is mentioned briefly in the Dies The Fire series, but it's not necessary to read one before the other.

Very good stuff all around. Meticulously researched and interesting from a simple historical perspective as well.