Part game and part advent calendar, the Flash-based Mission in Snowdriftland featured 24 levels--a new one opened up each day from Dec. 1 through Dec. 24--of wondrously wintry action.

Although this Extra Toxic-developed game was removed from the Web on Jan. 16, 2007, it reappeared a few days ago (on Dec. 1, to be specific)--seemingly to promote a bunch of DSiWare and WiiWare titles.
If you're any kind of platformer fan, I suggest you get your butt over to mission-in-snowdriftland.com pronto--before it disappears for another four years.