iCrossing's Rachel Pasqua says to grab a Web-enabled mobile phone (preferably a PDA or Blackberry), open the browser and type your site's URL in. What's the user experience like? What content gets deleted, what images and text remain? What's the navigation like? Is it an experience that you think your target market will tolerate?
Then do the same via Yahoo, Google or other search engine on the same phone. See what content the engines pull out, see if the site still looks good without Flash, or links -- and decide if your target market will tolerate that.
There may be only a small percentage of your market visiting your site via mobile -- but can you afford to alienate them with the imminent explosion of mobile?