Ever get a wheat penny in change from a purchase at a store? It is not uncommon. I quite frequently find them in the ''Give a Penny, Take a Penny'' pot at the cash register in convenient stores. I've even found silver dimes and silver quarters in my pocket at the end of a day of shopping.
You can go to any bank and get rolls of coins for face value, then search them for any old coins. Rolls of pennies often turn up many wheat cents and the occasional indian cent or war token. Rolls of nickels sometimes have 'silver war' dates and the occasional buffalo. I've even found Liberty 'V' nickels searching rolls of nickels. In rolls of dimes, quarters, and half-dollars you can find 90% silver coins. Even if they are barely distinguishable, they are still worth much more than face value for their silver content.
If you get to know your local bankers, you may even have them look for you.