bodies_in_motion

I do more than half of my workouts at home (before heading out to deskchair dayjob) and I don't have internet at home, so i can't rec workout videos but I can rec stuff you can do in a few square feet of clear space in your living room/dining nook (BTW, congrats for making space! Yay you!) that is good deskchair antidote, and both basic enough for beginner and adaptable enough that you can continue progressing or playing with variations for literally years. Whether anything keeps your attention or not has more to do with your attitudes and preferences than the material itself--different people groove on different stuff-- so no promises about that.
If video coaching makes a big difference for you, you can can probably find videos of whole routines incorporating these components, if that's what you want.

I'm a big believer in old-fashioned calisthenics or body-weight strength training, for strength, endurance, and cardio-respiratory fitness:
Squat variations
Split squats, squat lunges, and lunge variations
Pushups variations
Plank variations
V-sit or yoga boat pose
Crunches, bicycles, reverse crunches
Bird dog or yoga spinal balance
Bridge (w/optional leg lifts)
Reverse table or reverse plank
Triceps dips
Superman or yoga locust pose
Inchworm, elephant walk or bear crawl
Mountain climbers
Segmental rotation or reclined twist
etc.

Here is a website with videos of how to do many of these exercises (and other bodyweight exercises, filterable by experience level, target body parts, and equipment needed or not)
http://www.manvsweight.com/calisthenics-exercises/

Here is another site with a sample starter minimal-equipment workout (it calls for dumbbells; if you don't have dumbbells, you can use gallon jugs of water, or swap in a different exercise that works similar body parts):
https://stumptuous.com/the-less-thinking-more-doing-starter-program
More detailed explanation and progressions/variations on some foundational exercises (with video, if you have Flash player):
Pushups:https://stumptuous.com/mistressing-the-pushup
Squats:https://stumptuous.com/lurn-to-squat-good-e-zy

Here is a giant directory of exercises sorted by target body parts:
http://www.exrx.net/Lists/Directory.html
The same site also has a Beginning Exercise page:
http://www.exrx.net/Beginning.html
With a sample super-basic, minimum equipment strength training workout:
http://www.exrx.net/Questions/BasicProgram.html
(a sturdy dining table can be used in place of the bar for supine rows, or substitute another exercise)

Here's a 20-minute Youtube video of yoga for core strength that looks pretty good:
https://www.youtube.com/watch?v=PWlQ7Hf5DLk

You may be thinking: but I'm most interested in building lung capacity, don't I need to do more moving around to get breathing deeply?
Anything that requires sustained muscular exertion will also make your heart and lungs work to supply the muscles with oxygen. You can increase that effect (building lung capacity) by breathing deeply and slowly on purpose, rather than relying on reflex to manage your breathing. This can be done with any kind or degree of exercise, just as you can build endurance through any kind or degree of exercise by choosing the variation of it that requires moderate effort but you are able to maintain safely correct form, and gradually increasing the time you do it.


tl:dr: Calisthenics are great for non-gym workouts, and serve a variety of goals.