This power point presentation discusses a new way of mounting heatsinks, by using a combination of high thermal conductivity thermal compound and something called a "multiwall nano tube thermal mat". The so-called "thermal mat" is used between the base of the heatsink and CPU to fill in large voids. The University of Maryland research indicates that the best results are had by coating the heatsink base and CPU integrated heat spreader with thermal compound separately. In the author's tests, thermal joint resistance was lowered from 78 W/CM2 to 3 W/CM2.It's an interesting read.
FULL STORY @ SEMATECH (http://www.sematech.org/meetings/archives/other/20041025/Thermal/01Thermal_Bar-Cohen_TRC2004.pdf)