Younger:
Madeleine
The Little House (The little house first stood in the country, but gradually the city moved closer and closer
Dr Doolittle
Older:
Anne Frank: The Diary of a Young Girl
Red Sky At Morning
101 Dalmations (by Dodie Smith–NOT the Disney book)
Thurber’s The Thirteen Clocks. I was delighted to be able to snag it before any of my siblings when my folks started offloading stuff.
As I’ve said before, I first read the two Alice books when I was 13 and I have re-read them almost every year for the past 55 years. They still fill me with wonder and joy.
I still love The Chronicles of Narnia, The Hobbit, and A Wrinkle in Time. I won’t count Lord of the Rings, since I never finished it as a child and really consider my love of it to begin in '01.
Random, I grew up in northern Quebec and they had most of the Enid Blyton books at the local library. I moved to Massachusetts (Lexington) when I was 12 and started working at their library during high school (which is the biggest in MA after Boston Public supposedly) and they had a whole bunch as well.
But mostly I know about her because my parents grew up in India and they used to read her. My father used to buy me tons and tons of EB books whenever we visited there but in the Great Housemoving Sale of 2003 some bitch-librarian for a public school saw my books in a box in my room and was like “yo can I buy all of those for $50 for the school library?” and my parents in the rush, and because they are fools for public schools told her she could have them for free! For free! I’m still sulking over it but I intend to buy them all back next time I go home to the mothership.
AWESOME book, though I first read it in high school so I can’t really say it’s “from my childhood”.
Interesting. I had to pester my Irish relatives to get them. (Discovered them on a summer trip there when I was about 8 and was very annoyed to learn that there weren’t available here when we got back home.)
Chronicles of Prydain, The Little Prince (I swear I cry every time I read this), Flowers for Algernon (ditto), Maniac Magee.
Elizabeth George Speare, especially The Witch of Blackbird Pond and Calico Captive, which forever put me in love with costuming and the 18th century. Still good books, fifteen years later. The Velveteen Rabbit. Alligator Pie.
Lots of others that people have already mentioned.
Roald Dahl’s works are modern classicals. Especially Charlie & The Chocolate Factory.
Where the Wild Things Are by Maurice Sendak. Such a marvelous book and it still captures my imagination.
The Phantom Toolbooth by Norton Juster. Just recently re-read it and caught many references that I missed as a kid. My 10 yr old just recently read it as well and absolutely loved it.
The Lorax by Dr. Seuss. 'Nuff said.
A Penny a Look: An Old Story by Harve Zemach. A charming story that I think still applies just as well today as it did when I read it 30 years ago.
The Westing Game by Ellen Raskin. Layers within layers, an engaging puzzle with fun character accessible to kids as well as adults.
The original Three Investigators mystery series.
The McGurk mysteries.
The Henry Reed books.
The Westing Game by Ellen Raskin
My favorite book from my childhood.
cmkeller beat me on the simulpost. 
And it’s a damned good book.
Where the Red Fern Grows by Wilson Rawls. Made me (and my classmates) bawl as a third-grader when our teacher read it to us; made me bawl a couple of years ago when I re-read it 25 years later. It’s a simply wonderful coming-of-age story, with a couple of well-wrought life lessons.
Also, Ralph Moody’s Little Britches and its sequels, which are an autobiographical series of books on a young boy’s transition to adulthood in early 1900s Colorado. It’s quite similar to the Little House on the Prairie series, albeit set a few decades later, but written from a boy’s perspective.
Wow… reading everybody else’s choices brings back some memories, but as a boy I had a peculiar fondness for a certain genre of childrens stories and I think they’re all pretty good today.
Rascal by Sterling North
My Side of the Mountain by Jean Craighead George
The Boxcar Children by Gertrude Chandler Warner
Island of the Blue Dolphin by Scott O’Dell
The Sign of the Beaver by Elizabeth George Speare
The Coral Island by R. M. Ballantyne
Yep… apparently I hungered to live the rugged life alone with nary an adult in sight, well… what kid doesn’t growing up?
E.Nesbit’s series of children’s fantasy books, as well as** Edward Eager’s** more modern day versions, not only hold up well, they are both beautifully illustrated. Eager admired Nesbit and his books might have been considered imitations if not for his obvious respect for her.
Both are still in print.
I loved reading Shel Silverstein’s poetry to my kids when they were younger. I think I got more of a kick out of it than they did, and they loved his stuff.
My mother was English, and I had several Blyton books, including the Enchanted Wood and The Birthday Wish(?), the one about the girl who gets a trip to Fairyland on her birthday.
I also like the Encyclopedia Brown books.
For the uninitiated:
Sailboat