Chris Coyier checks out Sizzy, Polypane et al and decides which suits him best.
There are a number of these desktop apps where the goal is showing your site at different dimensions all at the same time. So you can, for example, be writing CSS and making sure it’s working across all the viewports in a single glance.
I noticed Andy Bell recommending Sizzy so I’m interested to give it a go. Polypane got Chris’s vote, but is a little more expensive at ~£8 per month versus ~£5, so I should do a little shoot-out of my own.