Did you know that taxonomies have descriptions that can be displayed on their archive pages? Me neither.
This is just one of those things that I didn’t notice for way too long. They can be pretty important for SEO on taxonomy archives, where Google is likely to spot a lot of duplicate content. Yoast says to make use of them, and I suppose he probably knows a bit about SEO.
If you need to support pre-4.1, add this to your archives.php template file.