In one quick and easy answer: Social Media… But there are so many different types, and ways to do it.
• Facebook and groups (always use pictures, they grab attention)
• Copromote (you share other peoples stuff, which gives you viral reach)
• Google+ (This is my favorite place. But be careful, they throw the spam gauntlet quickly)
I use all the above to promote my best-selling books, as well as my blog. I’m pushing for over 200k in the next few months. Crossing my fingers that I can make it happen.