I created a version of the card game, "Rummy" to help reinforce Major Keys and their relative minors. It also helps reinforce the order of the Circle of 5ths.
This would work well with students who have been working with the Circle of 5ths to test what they know. But for those just beginning, you might consider providing a copy of the Circle of 5ths showing the order and the relative minors. I'm planning on using this game all week with my students.
I kept it in black and white and just printed it on colored cardstock to save ink. I would love to hear if you would find this game helpful as well. I am making it available for printout here.