I have just connected a thick trail of dots which were lurking in my inbox without me even realising it.
In October, Authonomy invited me (and, no doubt, squillions of its other members) to be a beta-reader of its new site, bookarmy.com.
Bookarmy allows you to type in the name of a book you like, then provides other similar titles (based on its users' suggestions). It doesn't only show real, commercially-published books: it's got the wonderful Crack of Death, and Atlanta Nights--both gloriously bad books that were written as sting manuscripts to show that PublishAmerica will PublishAnything. And anyone who's a member can suggest links between books: all you do is search for a title you like, then add books which you think are similar to it.
That means that all sorts of self-published or vanity-published titles will appear on there if their writers register, and start building links. I've just linked Atlanta Nights to Crack of Death, to get things started. It's very easy to do.
But there's far more to it than that. HarperCollins has Authonomy, a site dedicated to writers, but can't make revenue from it; and they have BookArmy, a site dedicated to readers, who might be interested in reading new books, but can't make revenue from that one either.
They can, though, if they put the two sides together. By allowing the Authonomy writers to produce POD books, and the Book Army readers to buy them, they can earn from both sides. They have found a way to make money out of the slush pile. It's brilliant.