B is going through a phase again where he is obsessed with letters. He wants to talk about them, sing about them, put them in order, match them, and have them rescue each other. (This phase is WAY better than the dumping all of the letters out and walking away phase!) The Melissa and Doug letters are my favorite! I made this quick alphabet puzzle for him (similar to the outline mat and spelling mats we've made before).
You could also make these puzzles for upper/lowercase letter matching, putting numbers in order, or spelling names.