When I built The Confident Man Project website, I wanted to create affiliate links from keywords in the articles on the site so that I got paid when a visitor purchased a product that I recommended. Rather than inserting these links manually, I wanted them generated automatically so that all I had to do was specify the anchor keywords and my affiliate link.
So I reviewed all the plugins I could find, both free and commercial, that could generate affiliate links automatically from keywords in posts. The review took months(!), and I've just published the resulting comparison of keyword affiliate link plugins for WordPress on BuildYourBlog.net