Have Spacesuit, Will Travel by Heinlein is great. I've read it a couple of times now.

I've always meant to re-read the The Chronicles of Prydain (Book of Three, Black Cauldron, etc). I remember loving them as a kid, but I was probably somewhere around 10 when I read them. Has anyone read them as a adult?

I've read some of Pratchett's children books. The Tiffany Aching books and Truckers, Diggers and Wings. I really liked those, but they aren't that much different form his non-children's books since his writing is usually appropriate for most ages.

I've read some of Gaiman's too, the Graveyard Book and Coraline. I didn't really like them all that much. They were entertaining, but they were a little to simplistic for me, especially the Graveyard book.

Thief of Always by Barker is an very fun children's book to read as adult. I thought it was much better then almost all the books I've read by him. It definitely had the best pacing of the books of his I've read.