My nominations:

The Dresden Files -- Jim Butcher (seconded dreamiflame)
The Chronicles of Narnia -- C.S. Lewis (seconded morbane)
Discworld -- Terry Pratchett (seconded laurenthemself)
Young Wizards -- Diane Duane
Doctor Who and Related Fandoms
A Song of Ice and Fire -- George R. R. Martin
Greek and Roman Mythology
Highlander: The Series (seconded argentum_ls)