Hi Sarah, not sure which grade you need, but you can check out my Livebinder of resources for all elementary school subjects. Many links in math are also good for middle school students.
Have you looked at TenMarks?
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 you can browse by common core standard too. Be sure to check out the "collections" as well. I think you'll love it!
I will suggest you to check this site to learn more about math queries http://www.1to1tutor.org/, It will really help you.
Have you examined "Math Tricks"?
These tricks have mathematical calculations that promote using your brain, with sometimes help from a calculator, a pen, a paper and a friend.
You should try https://www.matific.com. It focuses on building mathematical foundations and it is free to schools.
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 posts on some queries younger students could try on this page which also has other sites you may find useful.
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 the mathematical concept.
You might want to check the website www.k-12math.info . It is an open resource with about 4,000 currently updated links to 1,000 of the most common terms used in OER elementary and secondary school mathematics materials. Links to materials available in CK-12, Khan Academy, AAAknow (formally AAAmath) and others. The website requires no typing to locate information, just several mouse clicks to obtain lessons, examples, class or homework activities and/or enrichment materials. The site has a top 5 star rating from Merlot.
Your preschooler is leaning alphabets. First School has shared a blog on it. Click below link to learn more about it.
A great free website to check out is https://www.matific.com. It offers over 1,000 mathematics episodes (interactive games) at the K-6 level. This website offers much more than a traditional game-like format, where the students are actually manipulating the objects within the game. I've used it in whole group, small group, and one-on-one scenarios. You can specifically assign activities to your struggling, on-level, and advance learners. Great tool for differentiation! Last but not least, the activities are aligned to the standards and many math book series.
-Lauren : )