I like taking a small baking pumpkin, cutting off the top and hollowing it out. Then I just put some wet florist foam in it, and make an arrangement with some fresh mixed flowers from the grocery store. I've seen these arrangements for $40-70 on florist web sites. I can usually get a pumpkin for $2-4 and flowers from BJ's (like a Costco or Sams) for $13. So I save a ton of $$, and people are always impressed.
It's really so easy to do even if you haven't arranged a single flower in your lifetime. It's almost impossible to have it turn out looking bad. I'll bet this would be a great project for kids to help out with.
I've done these types of container arrangements for various events....I've used teacups for a bridal shower and the pumpkin for Thanksgiving. I've been tossing around the idea of using a log for Christmas....but I'm not sure I really like that idea. I'm always on the hunt for my next floral arrangement container.