I dug the idea of countdown clocks that Risus Monkey blogged about so much that I made some record sheets. Apparently these come from Apocalypse World of which I now nothing. But as I understand it you use the clock to keep track of big happenings in your game world like war or plague.
Here's a sheet to track a single thing:
Here's a sheet to keep track of all the clocks running in a game world or region in one easy to see place: