I saw this sensory bin on someone's blog...I can't remember where! You put popcorn kernels, magnetic refrigerator letters and a scoop in a shoebox. I used alphabet stickers and put them on three separate pieces of paper and laminated them. A scoops the letters out and matches them to the letter on the paper.
When we started this, I kept the letters in three separate bags and we only did one page/bag at a time. Now A has enough interest and attention to do all three pages at once!
*TIP* When doing a small sensory bin like this, place it on top of a blanket. That way, when the little pieces (popcorn kernels here) fall out, all you need to do to clean up is roll the blanket and pour the pieces back in!