The Learner Song ("Focus focus listen listen")-Designed for Kindergarten students but I use it for first and second as well.
Books
In My Heart: A Book of Feelings | Read Aloud Story for Kids
The Legend of the Regulators
Hunter and His Amazing Remote Control
The Penguin Who Lost Her Cool
Don't Pop Your Cork on Mondays
My Mouth is a Volcano
Calm Down Strategies:
Belly Breathing
Count to 10
Think positive thoughts
Exercise (take a walk, go for a run, ride your bike, etc.)
Talk to a friend or trusted adult