30 Days of Yoga (YouTube)
Progressive practices for thirty days
Fitness Blender
HIIT, Pilates, and other workout videos. Also includes a series of routines for "people who get bored easily."
(Some videos require a subscription, but hundreds of videos are free.)
Planet Fitness Home "Work-Ins" (YouTube)
Routines designed for in-home workouts
Yoga with Adriene
A huge variety of yoga routines available through YouTube, with a declared mission to connect as many people as possible through high-quality free yoga videos that welcome all levels, all bodies, all genders, all souls.