There was recently a physics presentation at my University about thermoacoustics and its ability to be used for heatsinks. The basic idea behind it was that a thermoacoustic engine could be made to take the heat from the processor and convert it into sound, dissipating the heat more effectively than conventional heatsinks.
The
group working on the project already has a number of prototypes and showed some of them at the presentation and they were quite impressive! These 'engines' are already being made smaller than a penny in order to fit a number of them on a processor to increase cooling ability. And if you're worried about the sound coming out of them (the heat is converted to sound), the engines are converting it to high enough frequencies that it's undetectable to the human ear. They also told us that they're working on converting the sound back into electricity, perhaps to be used to cool the processor even further. I can't wait until these are commercially available...