Hundred-frames are good for showing numbers up to 100 in a different representation that matches the hundreds chart.
These cards are useful for quick looks/number talks (flash the cards for a few seconds and ask students "What did you see?")
Hundred-frames can also be used for open number lines.
Students can play the game of WAR with the cards. (Students compare the two frames and determine which card is larger).
These cards are a useful tool in any classroom.