I've found these blogs to be an invaluable source of knowledge, whether it's in regards to choosing the right cover art for your book or knowing what to price it at. Each one is a juggernaut of knowledge, and I've spent hours upon hours mining through each one.
Joanna Penn has a fantastic blog and also has perhaps the best podcast I've ever found for self-publishing. Her positive attitude (and adorable English accent) instantly made her one of my favorite gurus. Find her at http://www.thecreativepenn.com/blog/
Mark Coker, founder of Smashwords, focuses a lot on industry trends and detailing the best practices you should be using as an indie author. When I stumbled upon his interview on Joanna Penn's podcast, my career as a writer changed forever. Find him at http://blog.smashwords.com/
Jane Friedman started out in the traditional publishing arena, and has decades of insider expertise to share with indies. Whether you are traditional, indie, hybrid, or still working on your first book, she's definitely someone you want to tune in to. Find her at https://janefriedman.com/blog/
Some other gems include: