A lot of these I read when I was in my teens, but I still enjoy them:
Susan Cooper - The Dark is Rising Sequence
Madeleine L'Engle - Wrinkle in Time triology, and the others involving the Murray family. And I like how she pulls the Austin family from her other series into this as well.
Anne McCaffrey Pern books. Although I have never quite went beyond the initial three dragon books and the Harper series.
Hey, we're the same person! I love love love the Dark is Rising series and re-read it every few years.
Except I've read all the Pern books, so maybe I'm an alternate reality version of you. My mom read me the 3 YA Pern books when I was very small. My name is similar to Menolly, the main character, and I was hooked for life. I blame her for my SF addiction.