My son's chief interest right now is Pokemon. We've been taking a somewhat child led approach to unit studies lately, with me saying "What do you want to learn?" and then trying to accommodate L as much as possible. His first answer is always Pokemon, but we generally end up going with his second answer, since there are only so many things to learn about Pokemon. He's having a Pokemon birthday party in a couple of weeks, and I figured we'd do a fun little Pokemon unit afterwards, since we're getting him some new Pokemon books for his b-day.
I put together this little game for him, using cardstock, and Pokemon stickers. The gist of it is that I'll ask him to pick a card, tell me what the Pokemon's name is, and then have him try to find the letter that the name starts with, by sounding it out.
Now I know, your kids probably aren't obsessed with Pokemon. Maybe they like Thomas the Train, or Sesame Street characters, or zoo animals. This would be easy to adapt to nearly any theme, as long as you can find stickers that go with the theme.