I have seen a few "Print and Play" games that I thought looked interesting and I have even gone as far as printing a few of them out.
The other day on Wil Wheaton's Tabletop the featured a game called "12 Days". It's Christmas themed and based on the song. It looked like a lot of fun for a fairly simple game and I had a family Christmas party coming up in two days.
After a quick search, it was apparent that I was not going to locate a copy of the game in time for the party. However, I discovered that the publisher Cheap Ass Games had the game available as a free print and play version. I printed out the pdf files on a color laser printer and then checked through the house to see what I could use to make some sturdier cards. I found I had two sheets of poster board from the dollar store that were big enough to do all the cards.