\It’s not too hard! I was writing up a demo and figured I might as well share it with the world. You can do it in CSS or jQuery, definitely useful for galleries.
UPDATE: Just use Justin Tadlock’s Cleaner Gallery plugin. I am in the midst of rewriting my WP theme WPFolio Two. I wanted to make the gallery thumbnail images a flexible width rather than their default fixed width. To do this, I gave the attachment images themselves a width: 100%; but needed to apply my responsive […]