I first read about Cash Cow lite on Teach Science and Math. I downloaded the free version and DS8 started playing.Within a few minutes, I made my second math app purchase. Ever. We bought the full version of Cash Cow.
My son's description: "You add coins together to make bigger amounts: .05, .10, .25, 1.00. If you get to higher levels you can add glowing coins together to get more money. When you're done with a level you get to buy things for your farm."
It's a great little game for identifying coin values and putting various combinations together to produce higher valued coins. The game hasn't lost it's intrigue after accompanying us to a lot of basketball games. I, too, find it fun. We've definitely gotten our $.99 out of it.
Check out other math apps I've reviewed. The majority are free.
. You can also purchase/download the MP3 of 
for less than $1.
first establishes that one jellybean costs one cent. Text and color photographs then demonstrate a variety of coin combinations that equal amounts up to 25 cents. We practiced counting by fives and tens as well as counting coin amounts for numbers up to 25. Both children followed along, the 4yo counting jellybeans and the 7yo counting coins. A natural extension would be to follow this by "playing store." While it appears that this book is out-of-print (OOP), 
seems to have much cheaper copies.
by Rozanne Lanczak Williams brings coin counting to a slightly more advanced level. Coin combinations total amounts up to $1. A few rhymes encourage kids to guess what's coming: "One penny, two opennies, three pennies, four. What will we get when we add just one more?" Children can think in terms of trading...how many nickels or dimes equal a quarter? A fifty cent piece? A dollar? My kids did a lot of counting by 5s and 10s. The last page pictures a wide assortment of coins. What total do you get? (We counted $3.)
by Lillian Hoban, Arthur decides to wash bikes to try to earn the remaining money he needs to buy a shirt and hat for his frisbee team. He learns that you must "spend money to make money" as he forks out cash for soap and other washing supplies. The text provides opportunities to add and subtract amounts under $5.
tells of humorous, fictitious, class fundraising. Readers can keep track of expenses (such as $2 to "pay five younger brothers and sisters to borrow their wagons which had been our wagons in the first place") and profits ("no dollars and no cents" when the cat falls in the lemonade bucket) right along with the second grade. The tale takes a wild spin when a runaway vehicle from a class car wash inadvertently stops a bank robbery in progress. The reward money, or the promise of it, sends the class on a trip to New York.
by Nancy Kelly Allen is one of our favorites. Farmer Worth grows a very strange tree. Each year, with different types of fertilizer, the tree grows different types of money: 100 pennies, 100 nickels, 100 dimes, 100 quarters, etc. ...even sprouting Chinese Yuan the year the tree is fertilized with Chinese panda patties from the zoo. It's fun to keep track of the value of each year's crops. After reading this book, my son later referred to one of his discoveries, "Remember, 100 nickels is $5!" Get a 
. You could read "Shapes," by Shel Silverstein in his book, 
. Or you might consider using the hilarious poem, "Smart," (also by Silverstein in 
, 
