I just wanted to say how nice it is to see such a positive exchange between strangers on the Internet. Seriously, not only was this article (list) motivating and well-drafted, the tiny little community of readers truly were a pleasant crescendo I found to be the cause of an inward smile. Thank you, everyone, and good luck to you all with your passive income efforts!! 🙂

In addition to an extra income stream, residual income allows you to diversify your revenue sources. Instead of relying on your standard paycheck, you’re earning money through the royalties of an eBook or the sales of an online course. Diversity of income gives your overall financial portfolio more security and depth. Similar to passive income, residual income gives you more financial stability, flexibility with your lifestyle, additional retirement savings, and a more robust financial standing.

“[T]he stream of continuing payments that are earned by Brad and/or Karen from the commissions (current and future) earned by the brokers within a book of business. Residual income arises from all sources of income relating to or derived from an identified book of business, including commissions earned by the brokers within that identified book of business from any source whatsoever.”
So, it all makes me want to talk to people about how "relevant" their passive income is to their professions, or to their hobbies. I think the music idea could be more fun. I think the teen coaching idea could be more rewarding -- feels more "professional," or feels like it could make the world a better place. I suppose I could put a little time into each, but I'll be getting busy with these skilled nursing shifts, so I want to use time wisely.
Write A Book - Once the initial work of creating the book is done, and you’ve spent some time developing an effective marketing plan, selling books can be a great way to produce residual income.  Once your book is available on a site like Amazon, you could receive a check each month for doing absolutely nothing. Obviously, the more time you spend marketing, the more money you’ can potentially put in you bank account.
Investing in rental properties: Another form of real estate investment, rental investments (i.e. becoming a landlord) could steer you down the passive income path of steady monthly rent checks that you can use to pay off a mortgage loan on the rental property. After the mortgage is paid off, those monthly checks go right into your bank account -- potentially for years to come. 

stREITwise offers a hybrid investment between traditional REIT fund investing and the new crowdfunding. The fund is like a real estate investment trust in that it holds a collection of properties but more like crowdfunding in its management. The fund has paid a 10% annualized return since inception and is a great way to diversify your real estate exposure.
Many people talk about passive income and create the impression that you never have to do anything to keep that income going. The truth is that you will normally have to keep your eye on things if you want it to run smoothly. For example Richard Branson doesn’t run any of the 400+ companies he started but he goes over the numbers each day to make sure they’re performing well and calls the CEO if there are any problems.