If you run multiple cloud providers in your shop and are looking at ways to connect them with virtual networks, then vCider with its Virtual Private Cloud v2 release has something you should take a closer look at. The service can help you create private links between the different providers, just like you can use ordinary VPNs to connect external networks to be virtually inside your data center.
For example, let's say you want to use Rackspace's Mongo DB service but want to use Amazon for storage. vCider will put encrypted tunnels between the two IaaS providers and give you private IP addresses for your traffic to traverse. One customer, a biochemical library, is running a Cassandra database in Holland and using AWS in the US for storage and has connected the two locations. They claim the latencies are small and network performance isn't an issue. Using vCider means you don't have to deploy OpenVPN or other equivalent solutions too, which in some cases provides a big boost in performance. The customer cited above saw a six percent improvement by forgoing OpenVPN.
New to the v2 version is a virtual network switch that can cloak your network access, so only traffic from the encrypted tunnel is allowed into your servers.
vCider is available now for any cloud-based instance of modern Linux kernels v2.6 and above. It is not yet available for any Windows instances. You can deploy up to eight systems free of charge, and prices start at $100 per month for up to 16 systems in a virtual private cloud. You can get more information on vCider here.