We found few interesting free responsive joomla 3.x/2.5 themes today. You can download them without registering or any other hassles. Enjoy the freebies for Joomla.
It is built on bootstrap and it is responsive. It has three column style. You can set arrange the columns in any order you want. It also has short codes for implementing the the bootstrap functionality into the joomla.
It is also built on twitter bootstrap and it is obtained lot of downloads it seems. Probably you may give a try.
YouBubble responsive free joomla template
This specific template does needs registration to download.