I'm very interested in health and fitness and often lose hours at Mark's Daily Apple (primal lifestyle and health blog): http://www.marksdailyapple.com/tag/dear-mark/

The Getting Stronger blog is another wonderful health and fitness blog which focuses on training the mind to thrive in difficult conditions, though it has really amazing insights on diet and training as well: http://gettingstronger.org/about-this-blog/