Traditionally, fantasy has been written by men for male readers, though women enjoy them too. With YA fantasy, it's usually female writers gearing their books toward women/teens. Some of the things I love best about this is because a) they generally feature strong women, or female protags who become strong and more independent over the course of the book; b) I want a little romance with my fantasy, dang it; and c) they're just plain good reads.
So here are a few of my favorite fantasy books and series for YA readers:
1. Goose Girl series by Shannon Hale: An interesting feature of this series is that each book follows the story of a different character. (The fourth book, Forest Born, is my second favorite in the series.) Another of her great fantasy series is The Princess Academy, which received a Newbery Honor award.
2. Crown Duel by Sherwood Smith: One of my all-time faves. I seriously love these books. Make sure you get the copy that combines Crown Duel and Court Duel. Some libraries still have them as separate books, but most now have them as one book combined.
3. Poison Study series by Maria V. Snyder: Strong woman protagonist, which I love. Her Touch of Power books are equally awesome. (See my review here.)
4. The Thief by Megan Whalen Turner: The series gets even better once you hit book two. Then it's amazing. And after getting to know the author, I'm even more enthralled by her books.
5. Graceling by Kristin Cashore: This one is really good, but I LOVE the second, Fire, but have sadly not yet gotten to reading the third, Bitterblue.
6. Tortall books by Tamora Pierce: There are plenty of them to keep you busy, though the sub-series of Wild Magic is my favorite. But start with the Lioness trilogy.