Really depends on what you mean with webapp... if you say hostgator I suppose you are talking about a PHP website. It's been a long time since I last used one of those services, I now host everything on my Rackspace VPS. For ~15$ each month I have a VPS all for me wich I can manage as I want.
Otherway I heard a lot of people saying that Heroku (Ruby, Node.js, Clojure, Java, Python, and Scala)is very good. Or Google App Engine (Java, Python, Go)