Card games - addition war, multiplication war (stack a deck of cards in the middle, each player draws two cards, add or multiply, highest answer wins everyone’s cards, repeat, when the deck is out, player with the most cards wins). Subtraction war - subtract lowest card from highest, lowest difference wins the round.
xtramath.org - free, a bit dull, but each practice session is quick, plus it tracks your progress and moves you on when ready