Responsive layouts using media queries and CSS on the web are exciting. Many Mockups users are doing responsive layouts on their projects or are planning to. We've been talking with the Balsamiq community about how Mockups can work with responsive web design concepts, and we thought we'd explore some techniques that might help.
We wrote up a short tutorial with some techniques that may be useful if you're exploring how you will approach wireframing with responsive design in mind. I used the Bootstrap Symbols Library I blogged about previously as a grid system. Check it out and if you have other ideas, let us know!