Like many, many people I'm anxiously waiting for the July 21st and the publication of Harry Potter and the Deathly Hallows. But either pre or post Harry these fantasy authors also deserve to be read:
Diana Wynne Jones (my favorites; Howl's Moving Castle and it's sequel Castle in the Air, there are rumors of a third book but I've not seen anything definite).
Megan Whalen Turner (I loved all three books The Thief, Queen of Attolia and King of Attolia and I will be crushed if there is not another book telling Sophos's story).
David Almond (My favorite is Kit's Wilderness, definitely a young adult title, dark, layered and complex).
Markus Zusak (I'm more partial to The Messenger, than The Book Thief, both young adult titles and both well worth reading.)