I have never set foot in a gym, but I suppose bodyweight exercise counts. I initially started doing some pull-ups haphazardly a few years ago because I thought the way my arms looked sticking out of a t-shirt was a bit embarrassing. I have never really been able to care much about sports, and usually after about half a year I would stop going, but to my own surprise I enjoyed simple bodyweight workouts and have kept at them. I kept reading up on more information and expanding and improving my workouts.
In short, it turns out this picture that Xant posted is pretty much what I have been doing reasonably seriously for about 1.5 years now. Seems like a very nice piece of condensed useful information, I can recommend this to anyone, it is quick, effective and very easily possible to do at home. I just have about 5 square meters of free space in my room and a wall-mounted pull-up bar. The only thing I cannot really do at home as of now are dips, and I like dips, but I think I still scrape a pretty good workout program together.
These are the exact exercises I do currently:
1. Freestanding handstand practice
2. Archer pull-ups
3. Pistol squats
4. Bent arm stand hold or wall handstand pushups
5. Archer pushups
6. L-Sit or Dragonflags (nearing full ROM, yay finally)
7. Jump Lunges
Pretty much all of these in 6-12 rep range, aiming for time under tension of about 30-40 seconds, and 3-5 sets. I do 1+2, 3+4 and 5+6 together in circuit with about 30 seconds rest, giving me 1.5-2 minutes in-between sets of the same exercise, while still keeping my workout nice and quick. Additionally I do five minutes of wrist and shoulder preparation, since I have had a shoulder dislocation and issues with forearm splints, and a quick Ido-Portal-ish warm-up of about five minutes. Depending on how anal I am about the clock and whether I take fun exercise detours, I take about 50-60 minutes usually. Three workouts a week.
No travel time, no waiting for equipment, 3 hours a week from start to finish. It keeps my metabolism nice and fired up, allowing me to eat whatever. My functional strength is much better, this type of exercise provides a great basis for gymnastics, climbing, swimming, martial arts, etc. I am happy with the way I look, nicely balanced musculature. I am pretty sure you can make far quicker size gains with a solid free-weights program, but I think the effort/benefits ratio of my current routine is fantastic.
Recently started taking flexibility work way more seriously. For the future I plan on starting a straight arm handstand press progression as soon as I get a decent pancake stretch, and from there on out I hope to eventually reach my goal of doing a planche. Also going to take up grappling or BJJ as soon as my classes conflict less with their class schedule.