I use a griffin aircurve, which is essentially a universal dock, and comes with adapters that fit devices larger than the 3g/3gs that I use to dock with a case in. The feather should dock fine since it's not too bulky on the bottom to sit properly.
I have the Jr. version (charging only) and it works great. I'd imagine any case that doesn't cover the dock connector (obviously) would fit. iSkin Solo works fine.