Take a month of martial arts training (aikido, jujitsu, and judo are popular soft styles, Tae Kwon Do and Krav Maga are two very different hard styles (TKD is fun and mostly useless for defense, Krav is super effective for dangerous situations but pretty grueling)).
Join the local swing dancing scene. If you don't have one, try salsa or Argentine Tango.
Take an art course. Start with a beginner class that does a little with lots of different of media types, then take a class focusing on the medium you prefer. Do this even if you feel you are bad at art. I am terrible but I still enjoy working with clay.
Buy an Audible subscription and fill useless hours with audiobooks. This can improve commutes and other boring tasks.
Buy either a stereo Bluetooth headset with playback controls on it, or a small mp3 player such as the Sansa Clip Zip that has easily accessible controls outside your pocket. This advice is mostly relevant if you listen to media a lot. Having playback controls very accessible lowers the activation energy of starting your music/podcast/audiobook.
I recommend boxing. Every martial art tries to simulate a different aspect of real fights, and boxing simulates the speed, intensity and scariness of them by banning kicks and grappling which generally slow down a sparring, at least between beginners. Grappling is a lot like "now stop and think what's next" and kicking is a lot like "wow beware that leg, keep my distance", but if people are only allowed to punch, it is highly intense storm-of-fists experience.
This is also fun, and scary, and also great at building courage and a fightin...
What can I purchase with $100 that will be the best thing I can buy to make my life better?
I've decided to budget some regular money to improving my life each month. I'd like to start with low hanging fruit for obvious reasons - but when I sat down to think of improvements, I found myself thinking of the same old things I'd already been planning to do anyway... and I'd like out of that rut.
Constraints/more info:
Background:
This is a question I recently posed to my local Less Wrong group and we came up with a few good ideas, so I thought I'd share the discussion with the wider community and see what we can come up with. I'll add the list we came up with later on in the comments...
It'd be great to have a repository of low-hanging fruit for things that can be solved with (relatively affordable) amounts of money. I'd personally like to go through the list - look at candidates that sound like they'd be really useful to me and then make a prioritised list of what to work on first.