A few ham radio sites and blogs I've looked at recently had ads in the sidebar for ham radio equipment being offered at eBay. I thought this would be rather a nice addition to my own site, but I haven't figured out how to get them. After Googling "eBay ads" I subscribed to the eBay Partner Program, which appeared to be the thing to do. However, the ads I got were not terribly interesting from a ham radio point of view.
After a bit of further investigation it seems that the eBay auction ads I have seen are coming from Google. I have had Google ads on my site for years but have never seen an ad showing ham radio items from eBay displayed there. It's a bit of a mystery.
Postscript: Mystery solved. I finally got the auction ads to appear by telling Google I wanted image ads only, not text and image ads.