This is a very simple game that Zeke and I play using the white board magnet letters, although it could easily be played with foam, cardboard, or any other letters you might have. First I find a lowercase letter and moving the letter say, "Mommy, mommy! (or Daddy, daddy!) Where is my Mommy?"
Then it is Zeke's job to find that letter's uppercase match and rejoin it to its "child".
We continue until all the letters are matched and in alphabet order. I try to alternate matches that look the same (examples: s, x, or w) with matches that look different (g, h, q) since Zeke obviously finds the later more difficult then the former.
I especially like this set of letters because the upper and lower matches are always the same color, limiting the searching pool. If your letters are all the same color you might want to work with only 1/3 of the alphabet at a time, so the child isn't faced with 40 some choices each turn.