Well, you can certainly ‘dial up a desktop’ from any number of Desktop as a Service (DaaS) or Workspace as a Service (WaaS) providers but some partners and customers want to build their own.

A few good resource’s if your going down this road are noted below.

Dell Wyse Datacenter for VMware Horizon DaaS Reference Architecture

Learn more here!

and

Horizon DaaS (Desktop as a Service) Platform for Service Providers (Formerly Desktone)

Learn more here!

Finally, a must read for anyone heading down this road is the Desktop as Service book by VDI ninjas, Brian Madden & Gabe Knuth! You can get your hands on it here! Enjoy!