I have a cheap ass little switcher with just three inputs. I use them for Nintendo, Sega, and Sony. The Nintendo A/V stays in there, and I just switch them from the backs of the system depending on if I'm playing SNES, N64, or GameCube. Same goes for the Sony A/V for PlayStation and PlayStation 2. The Sega input is usually Dreamcast, but I'll unplug it sometimes for Genesis/Sega CD audio (and occasionally other stuff like the DVD player and MVS audio). I get the video for my Genesis/Sega CD from the RF, which is also shared with the NES. I have power strips to handle all the plugs. The MVS gets hooked up straight to the TV for S-video.

Sounds like a lot of hassle, but we've made it as easy as it can possibly get without spending the money for new things for the set-up.