audiobooksforfree.com has a pretty good selection
I clicked on http://www.audiobooksforfree.com/browse/Childrens/Grown-Up-Books-For-Kids and found Alice in Wonderland, Call of the Wild, some E. Nesbit short stories (she is a favorite of mine). Not bad, considering that these are standard stories in many classes. Check it out--for student or to try out yourself.
Same warnings about sound quality of the "free" version being poor...but bearable considering it's free! (I wouldn't throw over LibriVox for this site, though!)