I think EC2 ( http://aws.amazon.com/ec2 ) is a pretty good way to go but I'm interested in what others are thinking.
- You don't get a static IP address, so if your instance fails and needs to reboot, you might end up with a different IP address.
- If your instance fails, it also loses all the data stored in it.
- There is no hardware load balancing.
With that said, you can probably use it to complement your other servers by doing some of the batch processing.