Rock climbing is awesome! It's safe. It's a full body workout. You can do it both indoors and outdoors. No pressure, relaxed and noob friendly environment. You don't have to be very strong and the don't need gear to start. Renting gear at your local gym will do. Progress is measurable (as you get better, you'll find yourself doing higher grades of climbs).
All you need is a partner (guy/gal that you trust) and a local climbing gym. Go sign up for intro courses, that'll probably only take a day for the basics. It's really simple. The Boston area has metrorock.
Also, hackers will definitely make the connection between solving a "problem" in a route and regular problem solving. Most good routes (especially boulder problems) have a crux, where it's really difficult, but the way you get past is usually not by muscle-ing through but doing some unintuitive move that takes a leap of imagination and creativity. After some trials, you'll get the "aha" moment.
There's bouldering, which is low-height, and you fall on a map. A little more muscle strength required. There's also toproping, where you're climbing high walls but are protected by rope, and a partner belaying you from below. There are a few more styles that you can google if you really want to, that are not quite for beginners.
Tips (that you'll ignore anyway but then remember in the future):
- It's all about the fingers. After your first day, they will be very sore.
- Body positioning and movement is very important. It will reduce your tiring rate, and get you past positions where you can't quite get to the next hold. Watch other (advanced) climbers do their thing. Most won't mind. See how they move around fluidly and gracefully, and try to imitate that.
- Muscles will help later on but initially it's not as important as the stuff mentioned above. I have no muscles and I can pull of a decent 5.10-5.11 (ratings start at 5.6-7, and almost exponentially increase in difficulty to 5.15 for world champs.)
- Start easy, and try not to go up levels too fast. Many beginners fall into this trap where they already have lots of muscle and they can power through to the higher ratings. This is cool, but if you find yourself doing tons of arm-wrenching pull-ups and slamming your feet and knees into the wall, time to lower a level and practice a bit more until you get the sequences down perfectly.
- Practice falling. It'll reduce your fear of falling, and give you that extra boost of confidence to do that freaky move.