ExRx.net: While this website has been around for quite some time, it remains one of the most comprehensive exercise resources on the web. ExRx.net includes an extensive exercise library of over 1600 exercises as well as fitness calculators, weight management tools and more.
Live Strong Woman: a YouTube channel featuring free core and strength training videos as well as an "essentials" section with short video clips of specific strength training exercises.
POPSUGAR Fitness: PopSugar's YouTube channel features a wide variety of workout videos including the latest trends.
Trifecta Pilates: This YouTube channel features at-home Pilates workouts that don't require a Reformer or other expensive equipment.
XPT Life (Extreme Performance Training): Founders Gabby Reece, Laird Hamilton & Brian Mackenzie offer a website full of free fitness workouts (including instructional videos), recipes and lifestyle tips.
Subscription-based Streaming Class Websites with Free Trials: