At Metal Toad we're big fans of responsive design, but a common snag in the responsive planning process comes when choosing what device widths to design to. Just yesterday we had a big internal debate over what the best widths to design to are for 3 layout sites, 4 layout sites, etc. I'll get to our conclusions below, but another important distinction to call out is that for each layout there are two things to consider: what the pixel width range for a specific layout should be, and what pixel width the designer should create the PSDs at.
Our new site design is live, so if you're reading this in a feed reader, please click on through! In a nutshell, we wanted to redesign to take advantage of Drupal 7, HTML5, and dramatically improve the readability and usability of the site as a whole.