General

Active contains numerous articles on running, cycling, swimming, fitness, and general health tips.

Global Triathlon Network is a triathlon themed channel focusing on all aspects of triathlon, including videos about cycling, swimming, running, gear and training tips.

My Pro Coach is an online duathlon coaching site with training plans and free tips.

Active Training World offers free training plans for running, cycling, swimming, and triathlons.

Well by The New York Times contains articles, videos, workouts, training, healthy recipes and tips on creating a fitness lifestyle.

Strength

Fitness Blender contains free full-length workout videos covering topics of strength, and cardio.

PopSugar Fitness offers fresh fitness tutorials, strength workouts, and exercises that help with healthy living, weight loss, and stress relief. 

HASFit offers free workout routines and fitness programs for all fitness levels.

Workout Hotel has quick and full-length strength and cardio workouts videos.

Coach contains various fitness articles and includes workouts for all body parts. 

Yoga

Alo Yoga offers free yoga classes and tips for better stretching.

Sarah Beth Yoga has free yoga videos to help you stretch, strengthen, tone & de-stress, these 5-30 minute yoga videos made for all levels including beginner yoga, prenatal yoga, and workout yoga.

Yoga With Kassandra offers weekly Yin Yoga and Vinyasa Flow classes for all experience levels.

Adidas Women offers a selection of guided full-body workouts including meditation and yoga.