Setting up responsive content within a responsive theme I want to make a layout INSIDE the main content which is responsive.
I've read through dozens of pages, watched several videos and still there is no clear path to acomplish resposive content.
I started out with the latest Zen, but Display Suite and Panels let me place my fields in different grid layouts, but these grids end up not being responsive.

I now installed Omega, ending up having the same issue.
So, which theme and which modules let me setup a responsive grid WITHIN the main content?
If you are using Zen theme, best way(i hope so) to do responsive design is - Zen grids,
First u need to install ruby gems, after you installed u need two more things, as root install sass and compass and ofc. zen-grids

gem install sass 
gem install compass
gem install zen-grids


Then go to your theme folder, and write compass watch now all your css yo need to write in sass folder it will produce css in same files in your css folder. To do blocks responsive, in Layouts folder(ofc if you are using Zen sub theme) u will see responsive-sidebars.scss  or similar, now u need to import @import "zen";// Import Zen Grids with this statement. and write zen-grids code in your responsive-sidebars.scss. Read more about Zen grids - here.
I hope it helps.