One of my favorite holiday hacks is to use my coin jar to buy Christmas gifts. Our coin jar amasses quite a few coins by the end of each year, but I'm too lazy/busy to roll them up and take them to the bank. Instead, I take the jar to a Coinstar machine (there's one at a grocery store in town) and cash it in for gift certificates. Coinstar charges a fee to turn your coins in for cash, but turning them in for gift certificates is free!
Coinstar has a bunch of retailers to choose from — Amazon, Gap, ITunes, and more! (The Coinstar website contains a full listing of participating retailers.) I usually end up with at least $100 for Amazon, which covers a nice chunk of my Christmas shopping.
Brilliant. This hack is also great for kids and their piggy banks.