The Athena skin is designed to operate in multiple modes:
Mobile smart phones
Tablet devices
Desktop browsers
jQuery Mobile is another interesting approach:
I'm running a site with a (fairly) responsive skin
at
http://säsongsmat.nu (large thumbnails and image page images will resize, etc).
It's far from perfect, and some parts are more RD than others. One think that I
haven't looked into at all, is all the special pages that are build with tables
(Special:UserLogin and many more). Making custom versions of them all would be a lot of
job, so I'm asking here first: Has anyone done something like that already? I know
there are a few responsive skins out there, did any of them address the special pages?