Random thought 1:
Get a 3-channel or 5-channel sound system for your TV and/or computer. My father didn't know what he was missing until he did, and now he thinks it's great. Cost: $1000-2000.
(The reason we got one in the first place is kind of weird: my father likes to watch Blu-Ray movies, but many of them had sound that was totally out of balance: the sound effects were blasting but the spoken dialogue was barely audible. Online research indicated that this was partially a result of converting from 5.1 surround sound to stereo sound; in 5.1 sound, the sound effects come out of the side speakers but the dialogue would come out of the center speaker. Our surround sound system lets us turn up the center speaker and turn down the side speakers, fixing the problem, but before we got it, our hardware's conversion algorithms controlled the balance for us - and did it poorly.)
On ChrisHallquist's post extolling the virtues of money, the top comment is Eliezer pointing out the lack of concrete examples. Can anyone think of any? This is not just hypothetical: if I think your suggestion is good, I will try it (and report back on how it went)
I care about health, improving personal skills (particularly: programming, writing, people skills), gaining respect (particularly at work), and entertainment (these days: primarily books and computer games). If you think I should care about something else, feel free to suggest it.
I am early-twenties programmer living in San Francisco. In the interest of getting advice useful to more than one person, I'll omit further personal details.
Budget: $50/day
If your idea requires significant ongoing time commitment, that is a major negative.