One of my favorite websites is WeGiveBooks.org. The site provides free access to children’s picture books online, and for every book you finish reading on the site, the organization gives one print book to a charity that promotes literacy.
The site offers a mix of digital copies of classics and newer books you can read right on the site with your laptop or mobile device. A lot of our kids are on iThings anyway these days. Just route them to the site and click on Read to get started!