Responsive design is an umbrella term that regroups a set of techniques and technologies that enables website creators with the ability to craft sites that provides an optimal viewing experience for a multitude of screen sizes. This is mainly due to the proliferation of new devices on the market and there are no signs of this trend slowing down.
Most importantly, it gives the ability to design sites that will adapt and flow content based on the amount of display space available to maximize brand impact while not requiring a complete different site or set of sites to accommodate current and new devices makers may come up with in the future.
Here is a list of 8 websites using current responsive design techniques to provide great results and user experience.
Don't forget to resize your browser window to get the full experience. (^.^)
Get even more responsive: A responsive site about responsive websites.