How about a Geotargetting plugin for a custom landing page (i.e. same URL/homepage) based on defined locations/regions? Alternatively, redirect to specific URL.
Living social shows a different deal and background image customized to my location even before Iogin. Sometimes it detects a nearby city (Oklahoma City) instead of where I actually am (Tulsa), but once logged in, shows me the correct city for sure.
I might have the same homepage with a different background is all.
Or maybe a different set of content on the same homepage.
Or maybe redirect to a different URL for a landing page.
Or maybe integrate with a pop-over box.
Hope you like the idea as much as I do.