I’ve been dabbling with responsive web design for a while now, if don’t know what this means try resizing your web browser whilst on this site and you’ll see the page adjust to fit the size of the browser.
If you look at this site on a mobile you should see exactly the same content just in a different layout. Some people argue that responsive web design doesn’t work as well as a separate mobile site, but each website has different needs so it’s hard to give a universal answer but personally I love the concept. I suspect many people who don’t like it are agencies/developers who could previously charge for two sites instead of one site that works on both.
If you are new to developing responsive websites I’d recommend going across to .Net magazine and their ’50 fantastic tools for Responsive design’ article which will give you loads of opportunites to get the creative juices flowing.