If you've ever thought that you might want to own your own on-demand, pay-as-you-go, server in the (computing) cloud, Dave Winer has written a primer on how to set up Amazon's EC2 cloud computing offering.
If you run a single small Windows instance 24 x 7 for a month, it'll cost you about $90.
Hour to hour, it's 12.5 cents per hour. ;-)
And if you've ever bought anything at Amazon and have an account there, you're already an established customer - you just have to switch this on.