One of the fermented foods I love to teach (which is in my book and in my classes) is a low-tech Middle Eastern cheese. I learned it from my mom who learned it from my grandmother. It is salty and delicious and doesn't use a cheesepress and can be stored in a cool pantry in olive oil.
I think fermented foods were borne of both necessity and accident. Accidents showed people the possibilities and then the people ran with it.
Jenni, you can make "kraut" with various greens. I have used spinach and chard to make kraut. They're not as crisp as cabbage as the leaves are more "wimpy". The technique is the same and the results delish.
Natto is included in my book (and my online class). It is pretty easy to make but you have to provide a steady warmer temperature (room temperature won't do). This makes it out of reach for people who don't a dehydrator or some other means, but it is worth doing if you can. And I love that it can be made with any bean, not just soy.
Beth, no, I don't cover nukazuke. I would have loved to include recipes like that but the writing schedule was so tight I didn't have time to test everything I wanted!

--Wardeh ('Wardee') Harmon
GNOWFGLINS -- Enjoying "God's Natural, Organic, Whole Foods, Grown Locally, In Season"
Author of "The Complete Idiot's Guide to Fermenting Foods"