Free on-line books
http://www.magickeys.com/books/
http://www.tumblebooks.com/
http://kids.nypl.org/reading/Childrensebooks.cfm – list of the libraries
http://www.raz-kids.com/
http://www.storyplace.org/storyplace.asp
http://www.childrenslibrary.org – the best!
http://www.mobileread.com/forums/ebooks.php?order=desc&sort=dateline – e-library for bookreader