Although Amazon, Google and Microsoft are the big players, everyone and their dog are implementing clouds.<p>There&#x27;s even an open source cloud: <a href="https:&#x2F;&#x2F;www.openstack.org&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.openstack.org&#x2F;</a>  This is being used by some large companies (e.g. HP), and can also be used by companies who want to run a VM setup on their own hardware like they probably already do with VMware, but want a cloud-like API for it.