Cloud computing scared the crap out of me - the quirks and nightmares of provisioning cloud computing, dns, storage, ... on AWS, Terremark, Rackspace, ... - I mean, where do you even start?
Since I couldn't find a good answer, I undertook the (probably insane) task of creating one. fog (http://github.com/geemus/fog) gives you a place to start by creating abstractions that work across many different providers, greatly reducing the barrier to entry (and the cost of switching later). The abstractions are built on top of solid wrappers for each api. So if the high level stuff doesn't cut it you can dig in and get the job done. On top of that, mocks are available to simulate what clouds will do for development and testing (saving you time and money).
You'll get a whirlwind tour of basic through advanced as we create the building blocks of a highly distributed (multi-cloud) system with some simple Ruby scripts that work nearly verbatim from provider to provider. Get your feet wet working with cloud resources or just make it easier on yourself as your usage gets more complex, either way fog makes it easy to get what you need from the cloud.