ElderGym.com has a series of 12 leg exercises they recommend.
Yoga for Healthy Aging has a sequence of yoga poses for lower body strengthening.
Michelle Kenway offers leg-strengthening exercises particularly intended for women with pelvic floor issues, but I find them helpful and easy:
Ekhart Yoga has a playlist of yoga videos targeting leg strength:
Five Parks Yoga has videos designed to work your legs:
from Yoga Upload:
The following 2 videos are from one of my favorite channels Fitness Blender.