Threads on Zen Cart forums about recommended modules come around very often, but what is most intriguing about them is the wide range of "must-have" modules and the disagreements about what they are.
Since modules (plugins and addons) inhibit and raise the cost of upgrading, I strongly recommend that you use them only to solve problems or needs that you have on your site, to make your management easier and/or faster; and not because somebody else thinks they're a good idea or solved something for them.
A difficult question from Paddy Moogan in the UK: "Hi, what are your opinions on optimizing an Ecommerce website where the main pages or products may not necessarily be rich in content?" That's a tough question, right? Essentially, you're saying here's a place where you can buy products and there's not a lot of content or maybe the content is duplicated from a bunch of places. So, my short answer is, you know, put on your user hat.