I've used them for no cost nonfiction book promotion. It only has been a month, so it is a bit early to tell but here is what I did and what seems to be happening: I wrote several one page articles, taken from my books, added a couple more articles that were loosely related, and a couple more that didn't make the cut for the book. Six or seven one-page articles all totaled and submitted them to six or eight directories.
Here is one reference. I shortened up the introduction from my book: Woodworking at Articledashboard.com
This article is about how I stumbled across the idea for Builder Boards (the title to my first book): Builder Boards at Articledashboard.com
At the end of each article you get to put an about the article and, of course, I mentioned the two books I wrote.
There has been no incredible spike in sales or website hits. Maybe a slight increase in sales of one book. But when I google my titles those articles are popping up so there are many more references to my books. We'll see if there will be a more long term effect.
If anyone else has anything to add, or more long term experience, I would like to hear about it.
This is part of a series of articles provided by Nancy Burkhalter and Jack McKee following the February meeting on ways publishers can work together. Click on member suggestions in labels to see these articles and any follow-up.