Check out these links:
http://pelfusion.com/know-how/how-to-create-or-convert-website-into-mobile-format/
http://www.instructables.com/id/Create-a-mobile-web-site-with-RSS-CSS/
http://www.makeuseof.com/tag/create-instant-mobile-website-winksite/
Or automated:
http://bmobilized.com
Remember PhoneGap, where you can develop a mobile app for all kind of phones:
http://phonegap.com/