In my experience, just plugging in a monitor I've previously used will revert to the Display settings I last used with that monitor. So rather than needing to switch between recent display settings, I just need to plug it in and it switches automatically.
When I plug my computer into the DVI projector at work, it switches to 720p as the last-used setting with that projector, but when I use the external monitor on my desk, it uses the native 1680x1050 resolution.
I don't know if this works with VGA monitors, since I don't think the computer can actually identify the monitor(?), but would assume this generally applies to digital connections (DVI, HDMI, Thunderbolt).