I have a few hundred from Guys that went overseas in Army, Marines, Air Force, etc... You pick them up at yard sales and elsewhere dirt cheap, but, what do you do with them now...? Anyone.... Buehler
Depends on what you want from them. If they are modern circulated world coins they probably aren't worth much. Many coin shops will buy bulk coins for a tiny amount of money. Or maybe give them to a classroom or a coin club. When my kids were in elementary sometimes I would give a little talk on the history of coinage and let the kids each pick out a souvenir from a pile of world coins.
A tin of foreign coins and currency brought home from WW2 by my dad (Pacific theater) and my uncle (Europe) is what first got me interested in coins when I was just a wee lad. If not for that tin, I probably wouldn't be here today . . . I mean I wouldn't be here on CT, not that I wouldn't be here at all.
You start a collection. World coins by type either for a given country or the whole world is a collection you can work on for YEARS. And you can build a good sized collection for not a lot of money.
I have a couple ziplock bags of random new/old Canadian and Mexican type coins. If I can remember to put them in the car next time I'm around the ocean...they will get randomly deposited on the beach near the waterline.