If you're the sort of person who frequently witnesses the interaction between sweaty palms and slick plastic cases on expensive gadgets, you might find a product like Handstands' Gadget Grips interesting. Made of vinyl, the Grips attach to the back of any plastic device and are meant to a more tactile gripping surface to prevent those unfortunate slips. Palm Infocenter has a review; unfortunately, the Gadget Grips don't sound like they're best solution for everyone.