We use pallets for fire wood. An obvious use, but otherwise it means that we'd have to buy firewood. Many are made of oak, a nice, hard, good burning wood. You can even sell off some if you have that much.
We've also used to pallets intact to elevate things we've got stored but don't want to store directly on the ground. You can dissamble some pallets and use the slats to fill in the spaces of intact pallets for this. A really good use is under your washer and dryer. We've got one under our dog house too.
You can use the slats to build shelves for the garage or store room. Just sand them a little. some will need it more than others.
Or get “crafty” and cut out holiday figures like soldiers or candles, paint them in the holiday spirit and adorn your front yard! Have fun.