I haven't explored any yet, just figured it was the right thing to do. If someone wants to use rubber with another cloud, they wouldn't have too much work to do...hint, hint, nudge, nudge :)
W.r.t. dedicated or VPS hosts, I haven't done anything there, but if I were to be running my own VPS host, I would probably use eucalyptus to provide it with an AWS api, then just use rubber with that.
I probably wouldn't use any VPS hosts that didn't provide an api, and once it had an api, it shouldn't be too hard to add a cloud provider to rubber for it.
I guess if you really wanted to you could manually create the instance.yml file - as long as you aren't using ec2 features like elastic ips or ebs, bootstrap/deploy should work just fine.
Matt