Heroku – Paas provider which was acquired last year by salesforce. ”Given what I’ve seen from the Heroku guys so far I think they have a strong enough vision and understanding of their customers that they will be able to fend off the temptations of SF execs to meddle with their newly acquired toy.”

Google AppEngine – “AppEngine has long been one of the most feature rich platforms available. Yet, there have been two main issues which really held back what would have otherwise been incredible growth, performance and datastore.”

Djangy – “While AppEngine is a great platform for Python applications there has been pent up demand for a Python/Django version of Heroku. New startup looks to be the first viable attempt at filling that gap.”

I suggest to check those systems and Read more about their capabilities.

You are welcome to check also my up to date post about the PaaS market include more providers.