What do you need to implement virtual network and build hybrid cloud

To build an infrastructure that can be used to host a hybrid cloud environments or to benefit from the flexibility that a virtual networking provides we need software and hardware components. Below are couple of links I found when researching on this topic.

VMware ESXi/vSphere

• vSphere Distributed Switch
• Overview of vNetwork Distributed Switch concepts

Citrix XenServer

• Overview of XenServer Distributed Virtual Switch/Controller and Troubleshooting Network Issues

Opensource Linux alternatives

• Open vSwitch (IBM introduction and good overview of the product Virtual networking in Linux )
• Virtual Square / vde switch - Example how to use it with Rackspace Private Cloud Installing Rackspace Private Cloud - KVM or with  Virtualbox
• Linux bridge

Microsoft Hyper-V

• Hyper-V Virtual Switch Overview in Windows 2012

Vendors

• bigswitch networks
• nicira 
• 10 Next-Gen Networking Startups Ripe For The Plucking