"My school just began using IXL. It isn't free but they have more subjects than just math and it's really comprehensive. The kids can move through it at their own pace and if they make a mistake, the site goes back and reteaches…"
"Natalie mentioned Sumdog - that's definitely worth a look - good practice.
I'm a fan of WolframAlpha for all ages - even little ones as I think it can be so useful for students to check their work. I have included WolframAlpha's blog…"
"We've had some luck and engagement with SumDog Math - www.sumdog.com
"Sumdog's learning engine adapts its questions to each student's ability helping teachers deliver Common Core State Standards. Aimed at grades 1 through 8,…"
"Go to mathlanding.org. It is a new website of vetted elementary math resources aggregated from the web. And everything is free. The search engine is easy to use and there are lots of ways to find resources--advanced search is great and…"