Hal Higdon is an American writer and runner known for his training plans. He is the author of 34 books, including the best-selling Marathon: The Ultimate Training Guide.
He provides free training plans for 5K, 10K, half , full Marathons and more at https://www.halhigdon.com/training/.
A training plan app, RunWithHal 
, for your Android or Apple mobile devices can be found at
.
They come with a subscription fee. The app helps you design and track customized training plans.
Another resource is Training Peaks which sells training plans for a variety of sports. Many of the plans there are based 80/20 Endurance which is the creation of Matt Fitzgerald and David Warden.