What books should I get a little girl?

Second grade reading level is perfect to start the Little House books. Little House in the Big Woods is set when Laura Ingalls is about 5 (although the real Laura Ingalls was younger during the Big Woods years). The reading level of LHitBW is right for second grade, and there are more illustrations than in the following books. The reading level of the series increases as the story progresses, so little ones are able to "grow up" with Laura. I'd say they're pretty educational as well as obviously being American classics.

They're not strictly "educational," but Mary Pope Osborne's Magic Tree House series is a good blend of adventure, culture and history. My now-7-year-old stepdaughter devoured these when she was 6, and she also reads at a second or third-grade level. http://www.amazon.com/First-books-Magic-House-order/lm/R1586BRAOZXEEC to the first 40 titles in the series. My stepdaughter will often surprise us with random facts about the Titanic or the Civil War that she learned from Magic Tree House!

I love http://www.amazon.com/exec/obidos/ASIN/0590457225/metafilter-20/ref=nosim/ - but the Amazon review says ages 10 and up. I don't think there's objectionable content, but the reading level might still be a little bit advanced. It's a wonderful story though - fun, easy to read, and a the message is that women can do anything they want (so I think it fits the educational criteria).

The Clementine books by Sara Pennypacker are hilarious - kind of a modern version of Ramona. There are five in the series. Education value = human relationships, not much else, but fun. There's a series of chapter books about Disney fairies that I thought were terrible, but my girl loved them at 6-7 years old. Obviously, no educational value at all.

Betsy-Tacy!

My daughter who is about that age really likes the Boxcar Children books and the Mrs. Piggle Wiggle books.

I don't know any explicitly educational ones at that level, though American Girl has a series of books aimed at manners and skills for school-aged girls she might like. I figure school will create the association between reading and learning for my kids. What I set out to do is create the association between reading and fun for them as well. Junie B. Jones Series, Fashion Kitty, Captain Underpants, Bad Kitty, Skippy John Jones, Dragonbreath, Bone (a comic, actually), Squish (Super Amoeba), Goddess Girls, BabyMouse... these series are all a lot of fun and great for instilling a love of reading. Some of these will, um, not exactly be a tutorial on proper manners (esp. Captain Underpants) and might slightly induce silly kid humor and the occasional underwear joke. But my young readers love this stuff as a gateway drug to harder stuff later on... Also great for new readers, poetry by Jack Prelutsky and Shel Silverstein. I also like kid's joke books. These provide short bursts of fun reading and also make them more interesting at parties. :)

Seconding the Little House books. Also look into the All-of-a-Kind Family, which are sort of the urban equivalent of Little House books. James Howe's Bunnicula books are good, and very funny. I'd also recommend Edgar Eager (Half-Magic, and the sequels) and Michael Bond's Paddington Bear and Olga Da Polga books (which are out of print, but worth getting used). She's also right at the cusp of being old enough to read either the Baby-sitters club or Baby-sitters Little Sisters. They're of dubious educational value, but an eight-year-old I know loves them, and I did too, at her age.

Oh, another old writer to consider is Carolyn Haywood. She wrote the http://www.amazon.com/exec/obidos/ASIN/015205099X/metafilter-20/ref=nosim/. They're like the most whitebread vision of '50s America ever (though generally completely inoffensive), but they're kind of like delicious cotton candy for little girls. You know, cupcake dresses and flowers and puppies and things.