Tons of Bits have made an online advent calender with one level of platforming behind each door.
Indie developers including Amanita Design are providing free presents - complete a level and you get a download (avatars and wallpapers (so far))
And now Soundtracks as well
![Smiley](http://amanita-design.net/forum/Smileys/default/smiley.gif)
Try it out at
http://www.mission-in-snowdriftland.com/