Scalr - Roll your own server farm on top of Amazon's Web Services
I figured someone was going to do it before long, because I'd already thought this would make a great business (provided Amazon don't just do it and eat your lunch):
Put an easy to use console over Amazon's Elastic Computer Cloud (EC2) and Simple Storage Services (S3) for people who don't want to mess with infrastructure so you can focus on the dev side.
So, Scalr's web service is fundamentally a management, deployment and monitoring web console that sits on top of Amazon's EC2, EBS and S3 services to let you roll your own automatically scalable server farm with failover via web interface at just $50/m over the Amazon charges.
It even automatically deploys a master-slave MySQL instance for you and you can set automatic backups. Oh, and even private ssh keys get set up for you to download and log in. So, just use something like capistrano with a standard deployment recipe after this to deploy your app and you're off to the races. Oh, and pre-generates private keys for you to ssh into the server. Just download them and add them to your local deploy setup. Very cool.
Basically, seems to kick ass though I think you'd actually need to deploy and see how a non-mission critical site or application runs in practice to see if it works as advertised, but seems like a pretty cheap and very easy way to get into server farm deployment (and saves me from having my Systems team work up the recipes to do this automatically for standard setups anyhow).