What techniques exist for energy-efficient computing and networking?

I am currently reviewing the potentials of cloud computing regarding energy efficiency and green IT. In connection with this review I am having a look on techniques for increasing energy-efficiency in data centers (computing), hardware, networking and storage devices.

Specificially for computing/servers I have found already a few:

• energy-aware scheduling techniques utilizing frequency and voltage scaling
• virtualization to consolidate server resources
• energy-saving hardware, e.g. ACPI, several processor techniques, especially for mobile devices etc.

However, for networking devices it is rather hard to get information about energy-saving technologies. I have read that people are thinking about new protocols and alternative routing methods to be able to switch off hardware if the network is under low load. Does anyone know of such examples?

Which other points should be added, either for networking or computing?

Thanks,

emuba