Let's see: The Hardy Boys level is now considered MG.
Some of my current favorites are: Percy and the Olympians series, The Ranger's Apprentice series, and the Larklight series.
The first three Harry Potters are MG level. Then they creep into YA territory.
The Artemis Fowl books are MG.
Here is a link to
ARBookFind. You can search any children's book and it will tell you the reading level, word count, etc... Very helpful site. It's for parents and teachers, but it's dead useful to writers.