Starfall is an excellent website out there that teaches children to read. It's self-led, so all the child has to know is how to move a mouse and click. There are no external links, so parents don't have to worry about the child ending up on a store site. Both of my children will spend hours on the site if I let them, and the bonus is they're learning how to read at the same time.
My favorite part is that they can go anywhere on the site, even if they don't know how to read, and learn a little bit and have fun at the same time.
Go check it out!