[opdemand]

OpDemand is working on exactly what you're describing. Heroku-style private PaaS with emphasis on control over instances, routing layer, hosting providers, etc. Current version has full scaling support (instances, processes & nginx proxies). It's based on Docker, Heroku buildpacks all glued together via Chef server. It'll be released under Apache license. More to come...

[druiid]

I've seen your guys site before actually. I thought you were a Puppet house, not Chef though?

Sounds interesting to be sure though! I'll keep an eye on your site.