Ramona books were one of my daughter's favorites.
Mrs. Piggle-Wiggle is very funny, but because of the old-fashioned language might be a bit of a challenge yet. Perhaps that's one you could read together.
My daughter also liked a series called "Dinosaur Cove" but it's really geared towards dinosaur fans. ;)
Roald Dahl...Matilda, Charlie and the Chocolate Factory, etc...
If you can still find Babysitter's Club, those are great...there was the Little Sisters set too, but I never read those so I'm not sure if they're great or not.
Sweet Valley Twins...not Sweet Valley High... ;)
And as far as Dr. Seuss goes, I think the larger books like The Lorax, I Had Trouble in Getting to Solla Sollew, etc, are not only super fun but will help her reading skills improve even more.