There are an awful lot of math sites on the internet and too often, they are filled with distracting ads that make it difficult to find the learning material, or too many games that don’t so much teach math skills as babysit kids.
Here are some I’ve found useful in my technology lab. They’re straightforward, with an uncluttered interface (mostly) and a focus on teaching not entertaining:
Math and Virtual Manipulatives and Tessellations –well organized, using a whiteboard with shapes and colors as the virtual manipulatives.
Math website—popular, a standard 
Math—by Grade Level–a longtime favorite that reinforces basics, math facts and speed math
Math–Mental Math –traditional mental math practice. Well done.
Math–Minute Math –Mad Minutes
Games that make you think –logic, for K-3
Multiplication.com–lots of multiplication problems, lessons, games, with a few on addition and subtraction
Interactive Math Lessons–lots of them. You’ll find everything you need here.
Math problems by skill and grade
Jacqui Murray has been teaching K-18 technology for 30 years. She is the editor/author of over a hundred tech ed resources including a K-12 technology curriculum, K-8 keyboard curriculum, K-8 Digital Citizenship curriculum. She is an adjunct professor in tech ed, Master Teacher, webmaster for four blogs, an Amazon Vine Voice, CSTA presentation reviewer, freelance journalist on tech ed topics, contributor to NEA Today, and author of the tech thrillers, To Hunt a Sub and Twenty-four Days. You can find her resources at Structured Learning.
