Looking into ways of making web content accessible for mobile device users, I came across the following articles here and here

There is also a useful application for developers which emulates an iPhone here and a mobile version of the Opera Browser here

In terms of site design, the two main options appear to be either to write CSS which delivers an optimised version of the site to mobile browsers, or to create a separate .mobi version of the site for mobile users, as the BBC have done with their iPlayer