A more global set of statistics indicate that
1024x768 is indeed the most popular resolution, however the distribution of users is very different. Also note that netbooks, they suppose, are helping
800x600 hang on.
A web designer named Jon Hicks recently redesigned his website using them, go there and change the size of your browser window to see an example of how they work. There are layouts from 1- to 4-column, depending on your current maximum viewport width.
Media Queries allow you to not have to stress about things like "Will my site support the iPhone and iPad?" or "How can I target X device's screen size to maintain usability?". You just build designs for as many screen sizes as you want to support and the Media Queries will take care of the rest, depending on the user's browser when they get there.