Any coilovers that do not rust?
 

Are there any coilovers out there that do not rust? Or are springs the best option for regular street use?

Any high quality coilover will be built primarily of Aluminum, exceptions being the springs themselves, the piston rods and any fasteners.

I suppose you're worried about bad weather corroding them, a fair concern. I would personally get a high quality coilover and shoot some spray-on rubber coating on any exposed threads or fasteners (like Plasti-Dip or the Rustoleum stuff) to provide a thin protection against salt etc that can be easily removed with a rag and some thinner.

I covered my threads on the coilovers on my last ride with anti-seize, never had an issue with corrosion, and I lived in Chicago at the time.