So many books... so little time. I'm always on the look out for a new author or title, so I'm very interested in this thread.
Nearly every year or so I reread the Chronicles of Narnia books. Also, I loved: The Shack, To Kill a Mockingbird, Emily of New Moon series (by the same person that wrote Anne of Green Gables), A Voice in the Wind (Francine Rivers), Christy (Catherine Marshall), At Home in Mitford (the whole series - Jan Karon), and the Harry Potter series.
I have reread each of these books many times. They're like old friends!