http://www.distelli.com is another great company/service for multi-platform+multi-provider support. Dead simple to use. Discovered them a few weeks ago and it's totally upgraded my deployment and orchestration strategies.
You buy servers from multiple different companies, you install software on them.
Anyone can do that. I was actually wondering if there are software to automate this.
Openstack might allow you to do this.
(I haven't used it myself.)
Ansible is probably the best bet - once you have SSH it'll pretty much work with anything and it also has support for creation of servers on several cloud providers and stuff.
We use it for automatic configuration of everything from colocated hardware to $5/mo VMs on DigitalOcean and other low-cost virtual server providers and it works great.
You could use something like Terraform to help automate this. It's like CloudFormation but also supports GCE, Azure, DigitalOcean, etc.