BCCHardware just posted up a 6-way shootout of thermal paste to find out which one is the winner. They've got some of the big names represented and a few that you may or may not have heard of. Gelid, Arctic Cooling, Zalman, Arctic Silver, Tuniq and Noctua are all represented, but you'll have to check out their review to find out if there is a winner. You can read it over here.
The results are in, and they are pretty interesting. The biggest thing to note is that all 6 compounds we tested lowered the temperatures compared to stock cooling at least 2.5 degrees, however the gap between all of the compounds is only 2 degrees, which makes it pretty much impossible to say that one is better than the other. . .