One of the most powerful but lesser known features of CloudStack is it's ability to integrate with networking devices like F5 and NetScaler loadbalancers.
With CloudStack 3.0 you can deploy NetScaler with core Load Balancing rules. The core protocols like TCP, HTTP and UDP are supported and you can use the load balancing algorithms like Round Robin, Source IP and Least connection. It also supports session persistency based on Source IP and Cookie.
There's a nice overview of how that works over on the Citrix blog.
