A few months ago, I wrote a post on this same topic of Qigong/Chi Kung and Taiji/Tai Chi, where I explained a bit more about these low-impact exercises and how they can help you maintain and improve your overall well-being. You can read all about it here.
Now, I'd like to add a few more suggestions of videos that I have used myself - all, again, thanks to the great preparation work and selection of my teacher/master Ellen Hanes [check out more about Ellen and her NenChi page here, in Dutch].
You will notice there are a few favourite sources that have been used multiple times, so do feel free to follow them directly.
And let me know what your favourite videos are in the comments below :)
Mix & Match videos (English)
Super nice video to learn a lot about Tai Chi. The warm-up starts at 16:47 and it goes on for about 13 minutes, followed by other exercises.