Super Lube is great stuff...it's teflon impregnated and food-grade, believe it or not

. Chaos specs it for the poly bushings in their upper control arms.
Another great one is Green Grease, you can sometimes find it in the stores but easier just to order online. The wear and washout characteristics are even better than Super Lube, itself already a far cry from regular CV grease and the like. It's great for parts that need grease but must remain exposed to the elements.
www.greengrease.net, IIRC
I don't know if it is a silicone base, ie suitable like ntsqd mentioned.
-Sean