Here is one of my favorite songs about shapes. It also gives you the opportunity to count out loud. (It's a sneaky math/geometry song!)
(Tune: “Row, row”)
Square, square is a shape.
Tell me what you see?
Four corners. Four sides.
A square is what we see!
I cut shapes out of felt so we can count the sides and corners we are singing about. It also gives me the opportunity to ask the group if they can identify the shapes before I tell them what they are. I was surprised by a young two-year old who could identify all her shapes this week!
You could also sing with a shape-sorter toy or shape puzzle. Really any distinguishable shape would work.