A is for Mark and Angel Chernoff, a couple who write about simple living and happiness in their blog and books, the most recent being Getting Back to Happy.
B is for Becoming Minimalist by Joshua Becker, who discovered he was missing out on family activities because of managing all his stuff. He saw the light and starting becoming minimalist. He writes a blog and has published several books.
C is for Courtney Carver, who upon being diagnosed with multiple sclerosis, decided she needed to change up her life. She writes a blog, Be More with Less, and publishes books, most recently Soulful Simplicity.
D is for Shoshanah Dietz, a mid-life minimalist, who writes this blog, Mid-life Minimalist. She’s not nearly as well known as the others here but is working on it. She also has a group and page on Facebook to promote ideas of minimalism, simple living, habits, and happiness.
E is for Essentialism: The Disciplined Pursuit of Less by Greg McKeown, which has become one of the “go to” books in the area of minimalism. 
F is for the FIRE [Financial Independence Retire Early] movement and Personal Finance blogs and books that help followers minimize unnecessary expenses to achieve their goals (see Mr. Money Mustache, JD Roth, Kristin Wong, Ramit Sethi, J. Money, and more).
G is for Goodlife ZEN, a blog about happiness and personal growth written by a German-English woman living in New Zealand.
H is for the Happiness movement (aka positive psychology) and the people who write about strategies to bring more happiness into our lives (see Gretchen Rubin, Tammy Strobel, Tiny Buddha, Good Life Zen, and more).
I is for Ikigai: The Japanese Way to a Happy Healthy Long Life by Eric Goodfellow, one of several books on the Japanese way of living a happier life.
J is for Janet Luhr who writes the blog Simple Living and whose book, The Simple Living Guide, is a very popular guide to living simply.
K is for Rowdy Kittens, a blog by Tammy Strobel, who writes about happiness and tiny house living and has published the book You Can Buy Happiness (and It’s Cheap). 
L is for The Life-Changing Magic of Tidying Up by Marie Kondo, who introduced decluttering to a whole new audience.
M is for The Minimalists aka Joshua Fields Millburn and Ryan Nicodemus, best friends since grade school who eventually worked at the same company, made good money, spent even better money to end up in debt. First Joshua and then Ryan found their way to a minimalist lifestyle, and over the years they’ve created a blog, written several books, aired one of the most popular podcasts in the world, one documentary, and another soon to come. 
N is for No Sidebar, a website that publishes a variety of articles by different writers on minimalism and simple living.
O is for Optimal Living Daily, a podcast produced by Justin Malik, who reads aloud blogs about minimalism and related topics. It’s a kind of mini-audio book podcast, but with blogs.
P is for Project 333, the capsule wardrobe created by Courtney Carver (on her website), to simplify wardrobe choices.
Q is for Quirky Alone, a website, blog, and book about finding happiness your own unique way.
R is for Rightsizing Your Life by Ciji Ware and other books on rightsizing because it’s not about having a prescribed number of items, but rather finding what works best for your life.
S is for Elaine St. James, one of the most popular Simplicity advocates and writers in the 1990s.
T is for the Tiny House movement and the people who share their experiences building and living in tiny houses: Dee Williams, Tammy Strobel, Andrew Morrison, and a shout-out the tiny house programs on HGTV.
U is for Uncluttered, a course offered by Joshua Becker to help you get rid of the excess in your life, and for the many writers who help their readers tackle this step on their path to a life with less stuff, for example, Eva Schraub’s Year of No Clutter, Marie Kondo, Joshua Becker, Courtney Carver, and others.
V is for Vicki Robin, who along with Joe Dominguez wrote Your Money or Your Life, a guide to living your life with more intention and realizing the true worth of your time and life energy.
W is for Zero Waste Home by Bea Johnson, who encourages minimizing (to no) waste as we go about living our lives.
X is for Tsh OXenreider, whose blog The Art of the Simple, books, and podcasts encourage so many to live simple, rich lives and sometimes even travel around the world.
Y is for The Year of Less by Cait Flanders, who began by writing a blog, Blonde on a Budget, to discuss how she was getting out of a lot of debt and then published a book about her experience. 
Z is for Zen Habits, a blog by Leo Babauta, who writes about minimalism, habits, productivity and more.
RESOURCES
For more information on these and other resources, go to this page: Resources
Related Blog Posts
Love this list! What a great resource for anyone on the minimalist journey.
Thanks, Jennifer! I have a longer list on the Resources page of the blog (see menu bar), but I thought this would be a fun way to introduce some of the writers and add a comment or two about them.