The Ask Doctor Jo Youtube channel has some simple exercises and explains how to progress through them as your balance improves:
She also has a short video on ankle strengthening exercises and stretches. Ankle strength is important to maintaining balance.
This physical therapist suggests specific exercises:
This 8-minute Tai Chi routine is for improving balance:
This 20-minute video of standing yoga poses cultivates balance:
Yoga Journal offers this 14-minute practice on maintaining balance:
Melissa West has this helpful class with adjustments given for ability level:
More yoga for balance (28 minutes):
I subscribe to the Fitness Blender Youtube channel, even though most of their routines are either inappropriate for me or too difficult. I've found gold there. This is their Beginner Balance workout:
I do some kind of balance activity every day.