I’m a pretty big fan of Rackspace, ever since I turned to them to manage my dedicated servers years ago. I moved all my online activities to Rackspace’s new Cloud service about a year ago and I haven’t looked back. It’s been simply fantastic and I really enjoy not having to arse around with actual disks and physical aspects associated with servers (although I do use their Cloud Server facilities to spin up servers on-demand for some of the projects we have on the go).
CloudVox enables you to create apps in any language & deploy them on their scalable Asterisk hosting platform. I simply love the concept of being able to knock up a voice & SMS service in a few seconds that scales. If you’re a little bit handy with code, you can be live in moments. Love it.