If you want a good primer on the basics of marketing and small business thinking, I recommend "The Personal MBA" by Josh Kaufman. Having recently completed a degree in Business, I can see the parallels between much of the content I have learned and the content in that book. It won't be enough on its own to make you rich, but it does cover a lot of the fundamentals of microbusiness which you will benefit from knowing if you wish to make your side hustle anything more than a casual cottage industry.
If you decide that blogging is your thing,
http://www.problogger.net. I will of course gift you with the best thing I learned from that site: it will take three to four years of full-time effort to make a blog into your primary income, as a rule. Blogging is not an instant and endless money fountain.
If you are crafty,
http://www.etsy.com or similar marketplaces. Even just browsing around these sites may give you inspiration for something you are skilled at making, but you didn't realise could be your hustle.
If you want to try the online reseller route,
http://www.alibaba.com. Do be aware that going down that way will require a lot more capital and entail a lot more risk (because there is no particular reason why someone else cannot do exactly the same thing as you). This is the reason why ebay sites are not generally that profitable unless they work in volume, in a very niche market, or have a strong value proposition. Maybe skim through
http://www.reddit.com/r/flipping first.
Also
http://www.reddit.com/r/beermoney and
http://www.reddit.com/r/workonline. I cannot vouch for any of the stuff off reddit, but it's there.
My guess is if you don't have any skills of high value, it will take one to three years to develop a skill of sufficient value to make a decent pile of cash off it. If you already have skills of high value, and they're not being put to use in your job, you're underemployed and the first step is to seek better work. If your skills are being put to use in the job, you have three options for side hustlin': use the same skill privately (which may not be viable depending on the skill), use a different skill you already possess, or select and develop a new skill.
If you decide to go for a new skill, be sure it's one that is at least moderately valuable but is also at least moderately fun - you will be spending a lot of time on it, so don't get too enthused about something with big cash potential if you're just not interested in it. For me, this was programming. Looked interesting, and valuable, tried it -
hated it. Nope nope nope...
You don't really need a skill if you run a business of some kind. Every possible element of a business can be outsourced - all you need to do is provide some cash, the ideas, and the legwork required to arrange whatever it is you need done.
Don't buy a franchise. Franchising exists to make the owner of the business model rich, not the franchisees. My poor, poor cousin... If you want to operate a small business, buy one already in operation (lower risk but much worse return, at worst you'll have bought yourself a job) or start one up (much much riskier, but much better return potential too).
Online businesses are all the rage; thanks to the relatively small overheads, even a product with limited appeal can be profitable. I know someone who once bought a pdf guide to making sofa covers. Niche? Yes. Profitable? Yes. That $5 probably covered half the website's operating costs for the month. Sell three of those a month and the operator's making bank. The trick is finding something that you can make (or pay someone to make for you) that people will want to buy. I haven't figured that part out yet, and frankly even if I did I wouldn't tell you, I'd be out there doing it myself. This is the main reason you'll only find general business advice and scam get-rich-quick products online - why tell you or even sell you an idea that I could make more money off implementing myself?
If you want a crash course in operating an online store, there are websites where you can buy online businesses. You may get scammed, you may barely be able to keep a site going, but there really is no better education than plunging in and having a go. Just make sure you don't overcommit, of course.
Hope this braindump helped in some small way.
@anisotropy: ^_^
