This is a good video illustrating the power of manipulatives to help conceptualize numbers and relative amounts. It uses pennies.
Base ten blocks and other math manipulates also help with this. Here you see base ten manipulatives called basic operations pieces, complete with a ten thousand square. You can change the scale several times and work your way up to trillions. They are very useful for teaching exponents getting a handle on 102, 103, 104, as well as higher power algebra.
But as you see at Crewton Ramone's House of Math, lots of things can be used for math manipulatives including macaroni, raisins, and oranges.