Pass the buck
Give your child three pretend $1 bills; keep three for yourself. Pass one back and forth while you sing a song. Whoever's holding the bill when the song ends adds it to her pile. Play four more times, alternating whose bill you start with each time. Then help her count the money in each pile to see who won.
Bury coins in a small baking tin filled with sand, then have your toddler find them with a plastic spoon (or his fingers). Identify every coin he unearths, and have him sort his treasure into piles. (Keep a careful eye out -- coins are a choking hazard for kids under 3.)
Pay to play
Throw some bills in a bag, and have your child draw one out to find out how many times she has to jump: a $1 bill means once; a $5 bill means five times. Make up other challenges, like giving ten kisses or taking 20 big steps.
Who's the winner?
Lay out a penny, a nickel, a dime, and a quarter. Ask your child to find the smallest, the biggest, and the darkest-colored ones. Add another set of coins, and ask him to find the two smallest, biggest, and darkest-colored ones.
Tape two pennies onto two index cards, then do the same with nickels, dimes, and quarters. Turn the cards over, mix 'em up, and have your child match pairs by flipping two at a time. Ditch one set of cards, write each coin's name on new cards, flip 'em over, and have her match coins to their names this time.
Download photos of a $5, a $10, and a $20 bill from moneyfactory.gov/section.cfm/4 (or just do a Google image search for "dollar bill"; if the photos say "sample" or "specimen" in bold type on them, they're legal to print out). Cut them up into several large pieces. Scramble them, then have your child reassemble each bill. Let him peek at real bills for help.
Make some up -- for instance, "I'm orangey-brown, have Abraham Lincoln on my front, and I'm worth one cent. What am I?"
Fold a bill so just one part of it is showing -- say, George Washington's white hair on the $1 bill -- then gradually reveal more bits until your child guesses how much you're holding.
What's the difference?
Help your child compare the old $20 bill (the kind with a framed Andrew Jackson) with the frameless one that came out in 2003. See if she can figure out what changed and what didn't. Then talk about how the new version is harder to counterfeit because of its tough-to-copy green, peach, and blue background and watermark.
Make a meal
Let your kid go through the Sunday newspaper's grocery-store ads and cut out pictures of foods he loves, along with their prices. Challenge him to create a healthy dinner for $5.
Bottle full o' money
Fill an empty plastic bottle with coins, and have your child guess how much money's inside. Let her count it out to see if she's right.
Go the distance
Have your child lay pretend bills end to end to "measure" the distance from his bed to his door, or from the couch to the TV. Ask him to add up the bills' value to tell you the total "distance."
Line up some treats (fruit, crackers, stickers, erasers...whatever) and price them with sticky notes. Give your child coins, tell her to pay for what she'd like to buy, and let her keep her purchases!