First off all, I don’t like CSS frameworks unless you’ve created one for yourself as a starting point for projects. That being said, Less Framework 2 looks like it could be a good playground for playing around with and learning about CSS3 Media Queries.
Improve your design knowledge in just a minute or two a day, for free
Great Design Details
You'll get a free email every Monday to Friday with actionable design details that will increase the effectiveness of your designs. Each one only takes about a minute or two to read.