1. Hoggy-Hoggy-Hogwarts...er, that would be Harry Potter's world by JK Rowling in case you didn't know or have been living in a cave or something.
2. Cannery Row in Monterey, CA by John Steinbeck. Just go read my review to see why. :)
3. The strange and unusual world of 1Q84 by Haruki Murakumi...it may seem like 1984 Tokyo, but it so is not. I need to review this one soon!
4. The Fayz in the Gone books by Michael Grant, similar to Hunger Games, but set in present times and that almost makes it more terrifying.
5. Pretty/Ugly Town in the Uglies series by Scott Westerfield. Bubbly making hot-air balloons and floating ice rinks, what's not to love?
6. The Graveyard Book by Neil Gaiman (or any of his books really). This one is set in a graveyard, with like dead people and stuff. ;)
7. Xanth by Piers Anthony...full of puns and potty humor, but still an incredible, amazing, inventive world.
8. Narnia by CS Lewis...I always counted The Lion, The Witch, and The Wardrobe as the first book and truthfully, my favorite. It brings the world of Narnia to life. I need to reread this soon I think.
9. The Forest in Where The Wild Things Are by Maurice Sendak. This book and its illustrations will take you to another world.
10. Stoneybrook, CT home of The Baby-Sitters Club by Ann M Martin. Yes, it's the simplest world, but for me, the most real and the most ingrained in my brain (besides Hogwarts of course).
(thanks to Leah Riley for uploading this!)