1. The Mists of Avalon (Marion Zimmer Bradley) -- amazing retelling of the Arthurian legend from a priestess' perspective.
2. Foucault's Pendulum (Umberto Eco) -- opened my mind to the Knights Templar, Rosicrucians, and I seriously didn't know if this really was a work of fiction.
3. The Historian (Elizabeth Kostova) -- Dracula story within a story within a story told via letters and flashbacks
(Which reminds me of...)
4. Blood Groove (Alex Bledsoe) -- refreshing disturbingly awesome vampire tale (I so need to reread this!)
5. A Crown of Swords (Robert Jordan) -- "what? It's not over yet? How long *is* this series??!"
6. The Story of My Experiments with Truth (Mohandas Gandhi) -- I'd not actually known much about him, so reading this was eye opening, mind blowing.
7. IT (Stephen King) -- the only book that had me afraid of what might be under my bed.
8. The Stand (Stephen King) -- something about being sodomized w a gun barrel can make quite an impression on an innocent mind...
9. American Gods (Neil Gaiman) -- magnificent look at "gods" in these modern times
10. Chariots of the Gods? (Erich Von Daniken) -- read this in my very late teens, and my view of religions has never been the same.
So there you have it.
Feel free to leave a link in comments to your own list. If I have the time I'll take a look.