Ask HN: Where do you host medium-scale start up sites?

I have been using HostGator shared hosting as a low cost solution to host some of my start up ideas over the past year or so. Unfortunately any time a site gets a decent amount of traffic, my account gets disabled for server load or something of that nature. For those of you that outsource your hosting, what sites have you used that you like? My main requirements are PHP, SQL, ruby, and python.

Thanks!