I second Patron's endorsement of the role reversals Google group. Posting sometimes goes through slack periods, but the group has accumulated an amazing number of very interesting stories, considering how small and specialized it is. Patron is one of the best contributors, and the writer Seegee refers to, Bratdad, has tons of series on the site based on variations of the concept, though he rarely takes them to what you could call an ending. Be warned that the group's stories often involve minors taking control of parents and other adults. Explicit sex is avoided.
And if you're out there, Fatherjim, please come back. Your contributions to the group were always among the best.