mostly, there's so much to read that i don't get around to rereading things, with a few exceptions:

Borges and Kafka (especially his stories) get regular rereadings
Tolkein's Ring, every four or five years
Alice in Wonderland and Through the Looking-Glass
Wind in the Willows
Catch-22
Candide
The Odyssey
Robert Graves' retelling of the Greek Myths
and, lately, Asimov, Poul Anderson and early Heinlein (but only after a forty-year hiatus)

that's all that comes to mind at the moment.