At the beginning of each year on my supply list, I ask students to bring in a deck of playing cards. We use them all the time for drill and practice. Here are a few ideas.
Practice Problem- For whatever operation we are learning, I have the students use their cards to make problems to solve. For example, if I want them to add two 4-digit numbers, I ask them to turn eight cards face up and to arrange them into the 2 largest four digit numbers they can and add them up. The kids can pair up and the person who has the largest sum gets a point. The kids don't realize that after about 10 problems, they've done almost a whole worksheet!
Slap Facts- This is one of my students favorite games. Two students each lay down one card face up at the same time. The person who shouts out the product (or sum, or difference) gets to keep that pair.
Factor Go-Fish- This is like regular Go-Fish (Students try to make books of 3 or 4 cards), but instead of asking for 8's or 6's or whatever, the student has to say "Do you have any factors of 24? or 12?" Once they have 3 factors of a particular number, they can lay them down as their book.
Place Value Guess-- This is a fun idea to give students practice saying larger numbers. Students draw a row of boxes on thier papers that is nine boxes long placing the commas in the appropriate places (or 6 boxes long or to however many places they need to learn to say). The teacher then turns over one card and calls the number aloud. Students place that digit in any box they wish. The teacher continues to call out numbers until all boxes are filled. The student who made (and can say correctly) the largest number, gets to call out the next set of numbers.