I read a lot (my wife gets mad at me because I read so much faster than her), and these days I do most of my reading on Kindle. Fortunately there are ways to do this for little or no money. If you're interested here are some ways to get more ebooks without spending a lot of money:

1. Project Gutenberg is the grandparent of free book sites, with 60K+ public domain works.
2. MobileRead has an entire forum for fresh uploads of public domain works in Kindle format (they have other formats too).
3. The Libby app (iOS/Android) makes it trivially easy to borrow ebooks from your local library.
4. The Hoopla app (iOS/Android) is another way to borrow from your local library.
5. The Library Extension browser add-on (Chrome/Firefox) will alert you when a book that you're looking at online (say, on an Amazon product page) is available at your local library. (This covers print as well as ebooks)
6. BookBub will send you a daily email with books that are currently on sale at the major ebook stores.
7. I'm not sure how I got into this one; I think it was when I registered a new Kindle for Christmas. But in any case, Amazon is currently in the mode of offering me a $1 ebook credit on every order I have shipped, as long as I'm willing to take non-prime shipping and wait a few days. As far as I can tell this option is available on every Prime order, so I shamelessly take advantage. Need a $4 USB-C cable to replace one that's fraying? Hey, I can get it a few days later and add $1 to my credits. Until they stop this, I'll keep breaking every order up into individual single-item orders. It's not even worse for the planet, because their warehouse software recombines everything into as few boxes as it can anyhow.

Project Gutenberg is a great resource for free books, but its 50,000+ titles are intimidating in number (if not outright impenetrable). The same goes for other free ebook aggregators/feeds, of which there are many. There are also lots of authors who offer up their books for free. And, of course, there are tons of free options available in, say, the Kindle store. While it's nice to have so many choices, it hinders discoverability. Individual books get lost in all the noise.

As such, I'd like to know: what are some standout, recommended books that are available to readers for free?

Obvious disclaimer: I am not interested in pirated content.