Couple new themes added both responsive both clean and modern, so give one of these a go and get rid of your old non responsive theme already!
Bushwick inspired by Medium. Bushwick is a lightweight, responsive blogging theme, designed to show beautiful content alongside beautiful imager. *Add a featured image to your post to show on the left.
Features:
Fastr Clean and minimalistic content-oriented responsive theme for faster sites suitable for your personal blog. Fastr uses absolutely no javascript and has a very minimal CSS for its layout and responsiveness.
-Enjoy!