Courtesy of Wade W. Hampton and Knut Suebert: New hardware designs that plan to use Linux should take advantage of environmentally friendly technologies such as low-power CPUs e.g., the ARM from: Intel, environmentally friendly battery design, low-power displays (e.g., non-backlit LCDs), smaller packaging, etc. Linux supports a WIDE variety of hardware and technologies. These could be leveraged into powerful, flexible, environmentally friendly Linux-based solutions.
An "Environmental Rating" could be created for new Linux-based hardware and even some Linux-based software such as
bottlerocket (X10). Devices such as the Netwinder or the uCsimm would receive high ratings for their size, power consumption, capabilities, etc.
At Telepolis (German Computer Magazine) you might find an article about wasted resources during computer manufacturing.
Generally speaking PPC CPUs consume less power than x86 CPUs.