What are some alternatives?
When comparing Heroku and Apache CloudStack, you can also consider the following products
Microsoft Azure - Windows Azure and SQL Azure enable you to build, host and scale applications in Microsoft datacenters.
OpenStack - OpenStack software controls large pools of compute, storage, and networking resources throughout a datacenter, managed through a dashboard or via the OpenStack API.
DigitalOcean - Simplifying cloud hosting. Deploy an SSD cloud server in 55 seconds.
VMware vCenter - VMware vCenter Server provides a centralized platform for managing your VMware vSphere environments.
Google App Engine - A powerful platform to build web and mobile apps that scale automatically.
OpenNebula - The Simplest Cloud Management Experience