Our main site should format itself for mobile automatically using the CSS3 media tag. So theoretically it should be available on mobile right now :)

For non-smart phones there is the lite version, which I could send to more automatically. It does that now for textmode browsers, for example.

Then we have an iPhone/iPad app at http://duckduckgo.com/tools.html, with android and blackberry apps to follow. Those format the site natively and have a few other features, mainly extended zero-click where we grab relevant paragraphs from sites in real time.