My mom had a great little cross-stiched advent calendar while we were growing up. I remember being so excited to draw a little ornament out of the bag and hang it up to show that we were one day closer. I'm not ambitious enough to even consider cross-stitching... but I do want to do something. Here are a few ideas that I like:
I think the above is my favorite. Simple - modern - fun. I think I'll do some kind of variation on that.
Cute little matchbox advent calendar
Clever Gum Advent Calendar
Folded paper trees advent calendar
Pocket advent calendar
This one's such a great idea. You could sew these out of any paper, or wrapping paper and it would be easy, quick and cheap.
Misc. Paper Envelopes Advent Calendar - She also listed all of the activities that she put inside which is helpful for ideas.
Snowing Presents Advent Calendar
There's tons more online (obviously). If you're looking for more I found some good round-ups here, here, here and here.