I'm hoping someone can do the math on this: 

What if you liquid cooled your GPUs with hexane or water that heats up the hexane?  Make hexane steam (it has a boiling point of about 60C, depending on the type) to power a steam engine.  How much psi do you think you could get for an average high-end ATI card's waste heat?  I'm wondering how much electricity you could generate off of that heat.  I figure 1kw off of 150psi, just from looking around at kits and diy projects, which is roughly how much I'm using with my 4 gpus.  I'm rounding off a lot of numbers here though.