The following links (all free) are great ways to teach and reinforce basic/foundational skills.  I use many of them in the classroom. 

Free Digital Books
username: fannie
password: books

Jack Hartmann videos on various topics-count to 100, count by 10’s, subitize, sight words, letter sound and recognition, rhyming.  Many of the videos encourage kids to move while reciting and learning.

Sheppard Software- includes interactive games, both educational and entertaining.

 Starfall:  Helps teach letter knowledge, calendar, reading, math and science skill, too.  Also, has some more mindless fun.