CloudStack is open source software written in java that is designed to deploy and manage large networks of virtual machines, as a highly available, scalable cloud computing platform. CloudStack current supports the most popular open source hypervisors VMware, Oracle VM, KVM, XenServer and Xen Cloud Platform. CloudStack offers three ways to manage cloud computing environments: a easy-to-use web interface, command line and a full-featured RESTful API.
The new 3.0 beta binaries can be found here.
Just keep in mind that upgrades from any pre-release build to Acton GA is not supported, and should not be expected to work. This also goes the same for upgrades from 2.2.x to this beta release. Support for upgrades are planned to come in 3.0.1.