Bob asked on 1/22: "Should you use silicone grease rather than a petroleum based product to lube them?"
I'm assuming you're asking about urethane bushings. The Urethane guys (Prothane) recommend a "special" urethane grease that looks and feels like dielectric grease to me. I used it liberally on the inside of mine when I installed them (we're talking front beam, here) and they've been quiet since (10 years?).
http://www.prothanesuspensionparts.com/9.11110
On the rear torsion bar bushings, it seems like everyone except Mango Smoothie and me recommend talcum powder, while he and I use CV joint grease. Whatever you prefer.