Here is one of a few places I could remember out there that tell you how to design a page for mobile devices and making a webpage that can handle multiple devices.
http://dev.opera.com/articles/view/m...es-look-great/
I have been considering making theadultsearchengine.com multi device capable but haven't decided the best way to approach this. I could add all .wap pages to one category and have a .wap and .html version of the page or setup a .wap as a sub category to each of the categories I have and list .wap sites in there. Judging from the submits I have for pages like that at the moment, I might just make one category for portable devices until things pick up in that area.