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

abdodigital.com/login/
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.  

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=2ahUKEwjDwM2FnKzoAhV4l3IEHcrPAscQFjAAegQIBBAB&url=https%3A%2F%2Fwww.youtube.com%2Fchannel%2FUCVcQH8A634mauPrGbWs7QlQ&usg=AOvVaw3c--jJZuSHnHNPbbPVHMsl

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

 https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=2ahUKEwjjlpy3nazoAhVXhHIEHT19CskQFjAAegQIChAC&url=http%3A%2F%2Fwww.sheppardsoftware.com%2F&usg=AOvVaw1ycJr6Hndj4n5VVzQ9g2H9

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

 https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=2ahUKEwjg_4L1nazoAhUnkHIEHSZsDOEQFjAAegQIExAC&url=https%3A%2F%2Fwww.starfall.com%2F&usg=AOvVaw0G7dpvv6fiBcqPV07o_eaI