This is a much wider used marketing tactic than any other, but it also yields the lowest results. Forum signature marketing is using the signature at the bottom of your posts to sell products, for instance putting a link to a Clickbank product with the display name of the link as the name of the product. I have made a few sales from my signatures at websites such as DigitalPoint, SitePoint, and RevenueSource but it is only peanuts compared to what I've made through other sources. The problem with it is that you are marketing to a group of people that realize they are being marketed to, so the only way to turn a profit is to find products that they realize you are making a commission on yet they are still willing to purchase since it is something that they need to aid them in earning money. My favorite product actually converts quite well using this method, it is an ebook cover generator, I'll get into it below.