There are many members selling thermal grease under Garage Sales. You can go with Artic Silver, that's the best thermal paste ever made and it gives significant reduction in operating temperature of your CPU. It's good stuff.

Well, applying thermal grease need good skills, if you apply it too thick, it will be worst than before, it should be spread thinly and equally across the base of the HSF. Most people applied too much thermal grease until it leaks to the side. I've seen most pc shops doing that.