Come here for access to thousands of read-along books for emergent and early readers.  The site is called TarHeelReader and is actually designed for adolescent students just learning how to read.  However, many of the books would be appropriate for younger students.  The quality of the e-books is uneven, but you will have lots to choose from.  The topics are numerous as well: plants to Native Americans to the alphabet.  Overwhelmed by the variety?  Click the box in the upper right hand corner of the initial book link to select your favorites.  Children might be motivated to read and re-read with the help of the read-along voices, which also could be turned off.