Have in-depth knowledge in your niche? Package it up into an ebook and sell it on your blog. I'd generally advise against selling it (at least exclusively) on Amazon or Kobo, as you'll probably be able to charge much less. If you've already built up a solid audience, you can probably change anywhere from $5 for a very short one, all the way up to $39+.
Hi Sam! I love your site. We should definitely connect. I’m a school counselor and recently launched a site for parents to address pertinent teen topics. Like you, I struggle with the ultimate service I’d eventually offer on my site, but Ramsay’s idea is a great start. He’s absolutely right that people are looking for fresh content for their sites! Best of luck to you and I hope we can collaborate.