I'll throw in my pitch for the Smith "Sliders" series. I've taken stones, bugs, and all sorts of good stuff on 'em, and they've held up admirably -- that, and they're a damnsight cheaper than Oakleys.
Also, they have interchangable lenses like the Oakleys, htey come in a number of colors and lenses (including polarized) and they aren't quite as ugly (IMHO) as the Oakleys. They fit will under a full-face helmet, they're durable... good call all around. That, and if you snoop around on e-bay you can get 'em really cheap. There's a guy in Canada who runs a bike shop that'll usually give you a good deal.
--Jaeger
