An excellent slide deck describing experiences, common pitfalls and good practices of developing responsive websites: Pragmatic Responsive Design on Slideshare.
I was quite encouraged to see a number of my own practices being mentioned such as designing in the browser and augmenting the initial mobile stylesheet with additional rules only.
The BBC have been gradually investigating and adopting responsive web-design techniques to their news website, focussing on the mobile variant of the site. Initially I thought they were missing a trick by excluding desktop users from the benefits of responsive web-design. The reality seems much subtler however.
The BBC team describe their responsive approach on the Responsive News site.