Starfall is a great website that gets children in Pre-K, Kindergarten, 1st, and 2nd grade reading along with the story using interactive stories and phonics games.
Book Adventure is a free, motivational reading program available to children in grades K-8. Registration is required and it is free. To learn how Book Adventure works, click here: http://bookadventure.com/about_us.aspx
Reading Rockets offers strategies, lessons, activities and ideas designed to help young children learn to read. This website is ideal for parents, educators, and school staff.
Here are some great articles (from KQED.org) on how to help your children to read and encourage reading:
Surprising Tips That Help Kids Learn to Read
Steps for Cultivating a Love of Reading in Young Children
25 Books That Diversify Kids’ Reading Lists This Summer
The link below provides information on reading instruction (The "five pillars of reading").