We got this book at the library the other day, and it sort of sparked the whole thing:
One side is your standard letters and a picture of an object that starts with the letter, but the other side (it's a book you can start from either direction) is numbers, from 1 to 99, and an actual size picture of how many cents can make up that number. So, for example, the number 10 has a picture of ten pennies, two nickels, and one dime. I love that you can take actual coins and place them on top of the pictures in the book, so they can see the size and make the connection.
This morning August picked up the living room (including my things like all the shoes, or throwing away a diaper, I'm not just paying her to pick up her own toys!), and cleaned up her room. She earned one nickel and one dime (cheap labor around here, huh? LOL). Then we got out the book and found the picture of the nickel and of the dime and counted how many pennies were in each and added them together. She was VERY proud to have earned 15 cents!
I told her that when she earns a full dollar she can go to Target and buy one thing from the dollar section....we'll see if that's incentive enough to keep that room clean, but at the very least she's learning math! ;)