James Clear, the above author has the blog where he writes about habits extensively: www.jamesclear.com
Tiny Habits is a habit program created by Stanford Prof BJ Fogg - www.tinyhabits.com
21 Day Hero (shameless plug) - is a place where you start building habits through 21 day challenges. We're transitioning however to full-on habit building journey, through an app and other tools/programs - www.21dayhero.com
Selfication - http://www.selfication.com/ - is also a great blog in the behavioral science direction
Best apps out there is Fabulous, Spar!, Habitica, Pacifica and many others.
If you want this all in one - our team actually have this secret habit landscape map done, which includes all books, apps, researchers, blogs in the habit space. Haven't shared publicly yet. But can email it to you if you wish