Since I see some other fantasy lovers on here I'll weigh in (and since I'm bored and there are only 10 minutes left before I can go home from work!).
Lynn Flewelling - Nightrunner Series, Tamir Triad
Sarah Monette - Doctrine of Labyrinths series (first book is called Melusine)
Jacqueline Carey - Kushiel series
Robin Hobb - she has a bunch of trilogies that kind of make up a series: Farseer, Liveship Traders, and Tawny Man
Lane Robins - only two books so far but hopefully there will be more, there's no series name but the books are Maledicte and Kings and Assassins
I feel like I'm forgetting something important here. Hmmmm . . . Oh, I remember! Naomi Novik's Temeraire series is good, though I wouldn't call it one of my favorites.
and in the young adult/kid's world . . .
Susan Cooper - The Dark is Rising Sequence
and of course Harry Potter.
When I was a kid I also loved Patricia Wrede's Enchanted Forest Chronicles series and Diane Duane's Young Wizards series.
And, just to make a confession . . . My guilty pleasure is W.A. Hoffman's Raised by Wolves series. It's a self-published gay pirate romance series.

You can get them off Amazon.