Our advent calendar for this year - a vintage coke crate with boxes made out of newspaper, and (you guessed it) stamped with foam stamps.
Each box has some supplies for a craft activity for Ruby and I to do on that day, as well as a letter stamped on the inside which spells out a message when they are all turned over ("Merry Christmas Ru + Pep-Mae).
Here are some example craft activities - I still haven't done them all but I only have to be a day ahead of myself. A new stamp (I got the idea to use milk bottle tops from this post):
Some yarn, for making yarn snails:
Some fabric scraps: