My favored option is buying durable goods, especially labor-saving devices. $50/day surplus is enough to make one significant purchase (say, a laundry machine or a good-quality item of furniture) each month, for a noticeable long-term improvement in comfort. I don't like spending money in ways that will have to be repeated regularly.
That's my own plan for the next year, anyway; until recently, I spent my surplus paying down debts. (which, incidentally, you should do first if you have any, but I assume since you're asking that you do not.)
Do you have ideas for durable goods? My apartment has a laundry machine, and I can't think of a piece of furniture I would want.
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.