Even though I'm older I love Young Adult books. I enjoyed The Twilight Series and Harry Potter.
I also recently started the Divergent series. I've only finished the first book and I have the second one on hold at the library.
One of my all time favorite series is The Christy Miller Series by Robin Jones Gunn. I had all 12 books when I was younger and like an idiot got rid of them. I'm now trying to get them all back. The ones I had are hard to find as they're now in 4 volume books. If you have young girls or really any girl/woman would probably enjoy this series.
I pretty much love anything by Robin Jones Gunn. She's awesome!