Velociraptor is a Django- and Celery-powered web application for building and deploying software services. It is very opinionated about how this should be done, adhering (with one or two exceptions) to the Twelve Factor App methodology.
Velociraptor is language agnostic. It can deploy apps in Python, PHP, Ruby, Node.js, Java, Scala, Go, or any other language that runs on Linux.
Velociraptor supports zero downtime deployment for apps that include uptests.
Find the Velociraptor Documentation hosted kindly by Read The Docs.
Automatic tests are run here.
Gustavo Picon: velociraptor is BLISS
Mike Malecki: vr2 is pretty badass.
The tools are getting so good these days that custom PaaS systems are springing up all over. If Velociraptor isn't to your liking, you might take a look at Gilliam, Tsuru, or openruko.
You can ask questions about Velociraptor here:
IRC: #velociraptor on Freenode Google Group: https://groups.google.com/forum/?fromgroups#!forum/velociraptor-dev