dotCloud (http://dotcloud.com) is a paas that is natively multi-az. You can use that feature to reliably deploy ruby , php, nodejs, python, mysql, mongo, redis etc. It also has real support and a sustainable business model.
AppFog has "real" support (including live chat with all plans, including free plans). And the business model will prove to be quite sustainable (and bundled with a readily comprehensible pricing model).
(disclaimer: I work there)