I setup an Python Flask server on Azure last week. I was pretty impressed by the polish on a lot of the MSFT Azure management tools. I had also tried AppFrog, Heroku, and AWS Beanstalk in the past.

OpenShift also does Node + WebSockets now: https://openshift.redhat.com/community/blogs/paas-websockets

Modulus looks pretty good: https://modulus.io/

I haven't tried them out yet, but their support team has been very responsive answering my questions.

There is appfog, heroku, nodejitsu, and a few others. Afaik, nodejitsu is the only one with full websockets support at the moment.