Putting letters, or words in abc order or numbers in order. Cheap and brilliant! Great for skip counting, fractions, putting different three-digit numbers in order., all great ways to practice grade CCSS
Had when i worked in a preschool and kids love them! I would use colored sand instead of white salt. DIY salt tray with alphabet cards. Easy to make and kids have fun smoothing out the salt after correctly making the letter
Paint Bag Writing: Add some paint to a plastic bag, seal it up & spend the afternoon with your kids drawing designs through the paint. Using a Q-tip instead of your finger to avoid tearing a hole in the bag.