Here are directions to play Top It. All you need is a deck of playing cards!
And here are more math games to play with a deck of cards....
Pyramid – 1+ players (Found in Games for Math by Peggy Kaye)
Fan Tan (with multiple variations) – 2+ players (best with 4-6)
Builder’s Paradise (number sequencing)- 2+ players
Counting On – 1+ players