I've made a lot of small programs/games, but nothing that I felt I could charge people for much. I once made about $100 through ads in a blog after 6 months, but I don't think I'd want to repeat that route.
I have a couple of website business ideas, but they seem like they'd need a year to generate much income.
My best guess for things that seem to pay off the in the short term (The first month-ish) are: Affiliate marketing, solving buisness needs for people you know, and niche mobile apps (The kind that have few customers and charge $15+). If someone is more informed on this subject, I'd love to hear your suggestions.