So, whether for your wedding, a birthday or christening... even a company event or school exhibit, consider giving away things that can be used as coin-tainers. Mugs with pictures, sayings or logos will do just fine. Fancy dishes or small trays or cute bowls will also do. These will also hold pens or paper clips or other small things aside from loose change.
And if helping avoid litter isn't what you're aiming for, but actual saving, you can give piggy banks as well. Or, you can give away small clay pots and invite your friends/guests to save their coins in it, as leprechauns are wont to do with their pots of gold at the end of rainbows.
Cute gift idea eh?