Infrastructure for provisioning, billing & supporting webapps? Buy or build?
delano: If you're okay with US-only billing, you can use Amazon FPS in conjunction with EC2's product codes. The product codes allow you to build a machine image which you can authorize each of your customers to use and you can configure how much to charge per instance hour. Amazon keeps track of which customers are running instances and takes care of the billing details (you can do this with other aspects of Amazon Web Services too).If you require non-US billing, find a billing a system that gives you an API for post-processing hooks (this isn't my area of expertise but it looks like others are offering suggestions here). You can use the API hook to launch an instance at the provider of your choice (EC2, slicehost, etc...) and also send your customer the access info.With regards to provisioning, I suggest creating your own base machine image and scripting the minor customer or instance specific stuff. This gives you a balance between launch speed (you don't have to install the same stuff every time) and flexibility. If the scripting is simple, you can get away with hacking something on your own. If it's more detailed, I'd suggest Fabric (http://www.nongnu.org/fab/) if you're into Python or Rudy (http://github.com/solutious/rudy/) for Ruby.Note: I developed Rudy so I'm biased :]