Pennants/flags are popular and very quick and easy to made. I made one with 'Merry Christmas' appliqued on it for my daughter that I think she will use above the fireplace. I'm thinking of making smaller ones for the tree or for above doorways. You can spell out messages to Santa if you have small people in the family.
I also made yards of brightly colored flags for decorating the patio for summer parties. They didn't take long and you can make them any size you like.