Hi,
Here is a thread, on another forum, giving an overview of Thermal pastes on the market (it's a few months old)
http://forum.hwbot.org/showthread.php?t=71658
I personally use Arctic Silver 5 and have done for years - some say it's a little dated and there is better out there, but it's cheap and highly efficient in my opinion (I'm an IT engineer in RL, if that counts for anything!!

) and it keeps my i5 2500K nice and cool!