I have a promotional recommendation for any group of self-published writers here game enough to work together.
You must charge a minimum of $.99 for a book published to Kindle. If a group of you (preferably but not necessarily from the same genre) came together and chipped in enough sample chapters to turn into a 70,000-word package, you could offer it on Kindle, Sony, B&N, Kobo, etc. You could also package the collective work to go viral as a =free= compendium, then each of you could simply send it (probably as an Acrobat pdf) to everybody each of you knows with a request to forward it on to the entire world.
I do both with an ebook collection of samples from every book I have in print in my name, and a similar but not identical collection from books my publishing company has in print. Each collection includes direct links to my websites and I intend to add live links to the actual book pages on Amazon, Amazon Kindle, Sony, etc. I sell the collection of books I wrote for $1.00 on Kindle but will give away the pdf version to anyone who asks.
The collections have been out for months and I get inquiries or other email from faraway places like Australia and Russia.
FWIW, in 1999 I published a 2500-copy offset run of twenty sample chapters that sold out in a year. The POD edition still sells, and I have no doubt it still contributes to sales of other books from which content is drawn.
If you’d like one of the pdfs to see how I do it (or just to read my stuff), go to http://www.PacificaMilitary.com, click on the free book link, and save the file to your computer. This version does not yet have live links; that’s a few projects away.
All my Kindle books have live links to my sites. Sony scrubbed the links. You can reach my personal site on a Kindle via the link embedded in the Kindle ebook.
And on and on and on.