This article is from the Puzzles FAQ, by Chris Cole firstname.lastname@example.org and Matthew Daly email@example.com with numerous contributions by others.
What exceptional words turn into other words by movement of letters?
longest word allowing exchange of letters (metallege)
longest head-to-tail shift
longest double head-to-tail shift
longest complete cyclic transposal ATE-TEA-EAT (3)
Unless noted otherwise, all words occur in Webster's Third New International
Dictionary, Merriam-Webster, Springfield, MA, 1961.