Pedagogically sound games and animations engage students in developing understanding of math concepts!
As an adult, I enjoyed all of these games and animations and I can honestly same the same for my students. I wholeheartedly recommend this site both as a resource and as a teaching tool. They have teaching guides and listed standards for each game and animation, but don't feel restricted to only those which are officially at your grade level, as all activities are scaffolded and at the beginning levels can definitely be used by grade-levels below their official designation.
How I Use It
These games are aligned with 4th-6th grade standards yet I was able to incorporate them into my work with gifted 3rd graders for on-level, enrichment, and support tasks.
I used the game Gate to help my on-level students third graders reinforce their understanding of place value in the ones, tens and hundreds place as well as their understanding of multi-digit operations with basic factors (2, 5). Third graders eager for more progressed to further level, where they continued to work with multi-digit operations to the tenths or hundredths.
I showed my students the Atlantean Dodgeball animation on ratios and differences because I know that in upper graders there is confusion between ratios and fractions and I thought this easily understood and entertaining story was a great way to introduce my younger students to the concept.
My students absolutely loved Pearl Diver, which works with both placing whole numbers and fractions on the number line AND the concept of open number lines. So many student persist in thinking that number lines must start at zero! It's a fun, simple, and rewarding way to practice these ideas. I used the Number Rights animation, which has a learner's guide in addition to the teacher resource included with all the games, in conjunction with Pearl Diver. It's yet another accessible way to discuss how "to plot, order, and visualize quantities on a number line."
Monster School Bus, which works on fourth grade skills such as understanding the decimal notation for fractions, starts off easy enough that my third graders could easily use it. In addition to working on addition skills with whole numbers and then decimals, it also reinforces the invaluable skill from primary grades of find combinations that make ten.