Disclaimer/Warning: Only use this activity with children you are sure aren't putting things in their mouth any more. And even then, closely supervise.
I found cork squares at Joann Fabrics for about $2. Use a marker and draw shapes on the coasters. You could use cookie cutters to trace simple shapes. (I did dots, but if I were to do it again I would just trace lines.) Bring cork, pushpins, and the children to the table.
Introduce pushpins to children. Explain that pushpins are for grown-ups and children only get to use them during very special activities because they are sharp. Remind them that if they ever find them at any other time they should carefully bring them to a grown-up to put them away. This introduces basic safety rules and also has the side benefit of making the children very excited about the activity.
Let them use the pushpins to fill in the shapes.
Skills/Objectives addressed here:
Vocabulary/Concepts: Shapes, colors (we only had red pushpins, but if you had many colors you could address colors and patterns), patterns
OT: Fine motor / pincer grasp / hand-eye coordination
Speech: Use this activity as a motivator. The child gets to push a pin in after every X repetitions.
Pragmatic: Listening to directions, turn taking, attention span, eye contact