Interactive
National Council of Teachers of Mathematics

Nctm: Illuminations: Grouping and Grazing

For Students Pre-K - 1st Standards
A game that reviews grouping in fives and tens, and adding and subtracting. The instuctions are clear and include a video of how to play.
Unit Plan
Khan Academy

Khan Academy: Add 1s or 10s (No Regrouping)

For Students K - 1st
Practice solving problems like 34+5 and 34+50. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.