From Get Rich Slowly:
But if you really want to see your savings grow, donâ€™t just save your coins â€” save your one-dollar bills, too. If you come home with two or three dollar bills at the end of most days, itâ€™s easy to accumulate $10/week (about $500/year). Donâ€™t put your dollar bills into a jar, though; use an envelope.
TBWITWW and I have been saving change (we actually have 4 holders one for pennies, one for nickles & dimes, one for quarters, and one for state quarters we haven't sorted for the coin books) We don't use cash much, but I'm tempted to start adding dollars to this. Last time we cashed in change it paid for our rice cooker.