Impact of technology on literacy in early grades

I am looking for some "hard" data on how the integration/use of technology in early elementary school impacts literacy development. While there is much anecdotal evidence out there about the ways in which the use of technology engages and excites students, does anyone know of any research or data about how computers in elementary classrooms improve literacy (traditional or "new") skills? Even more specifically, does anyone have any data on how student achievement levels in technology-rich environments compare to those in more traditional classrooms?

I'd be grateful for any suggestions!