The Constellation theme is the perfect starting point for any WordPress project. It gives you the flexibility to provide bespoke styles for different devices, totally up-to-date HTML5 code which is fantastic for SEO, a flexible grid system on top of all the other goodness bundled in to the HTML5 boiler plate.
Take a look at the demo to see everything in action, resizing your browser window to simulate different devices like Netbooks, iPads & smartphones such as the iPhone.