Here are some wonderful websites that have games and activities to reinforce skills that students are learning in school.
General Math:
Facts Practice:
http://www.harcourtschool.com/activity/thats_a_fact/english_K_3.html
https://xtramath.org/#/home/index
Place Value
Pac Man Expanded Form : http://www.sheppardsoftware.com/mathgames/placevalue/mathman_place_exp.htm
Football Place Value: http://www.math-play.com/football-math-place-value-game/football-math-place-value.html
Addition
Multi-digit Basketball Addition:http://www.math-play.com/Addition-Game.html
Two digit Addition Memory: http://www.math-play.com/two-digit-addition-game%20-with-regrouping/two-digit-addition-game-with-regrouping.html
Multiplication Practice
Basketball Multiplication: http://www.math-play.com/one-digit-multiplication-game.html
Candy Capers: http://www.fun4thebrain.com/multiplication/candycapersmult.html
Multiplication Memory (x2): http://www.math-play.com/multiplication-game-times-table-2/multiplication-game-times-table-2.html
Rounding
Pirate Game: http://www.math-play.com/Rounding-Numbers-Pirate-Game.html