I wrote the following as a non-technical analogy for a variety of “as a service” cloud type providers.
AWS gives you the entire play ground, for the most part. You can do pretty much anything you want, and they give you some really cool pre-made toys to put in it.
Engine Yard is more like a sandbox. You can come play in the sandbox, but they make the rules and you have to use their buckets and shovels.
Heroku is just the bucket. You can’t look inside, you just put your sand in and they mold it into the sandcastle.
Rackspace is more like the entire park where the playground is. There’s other stuff there, and you can make use of it while you visit. They have a few sandboxes, and you can build your own section.
Opscode is like the construction company. We provide the tools and materials needed to build all the sandboxes, buckets, and parks. Each of the others can use Opscode in whole or in part of building their playground or park.