Trent Walton has written (and designed) a great (and beautiful) article on dealing with content in responsive web designs that adapt to the width of visitors’ browsers. Content Choreography is a good discussion of content organization, changing designs too much between various widths, and the workflow needed when creating responsive web sites. Definitely a must read for any designer or developer.
Jason Grigsby of CloudFour has posted an interesting (as always) article on the latest trends in mobile first responsive web design and the numbers show the majority of responsive designs provide very little, if any, file size savings for their mobile versions.
Seen it happen accidentally since nearly the beginning of the responsive web design movement, but great writeup on how CSS3 transitions can add some fun to your responsive designs.