If you’re looking for resources on Zen Cart, the obvious first port of call is the main Zen Cart site http://www.zen-cart.com. The site boasts a wealth of free add-on contributions, tutorials, wiki documentation and a very busy user forum.
I’ve come across lots of other websites that have resources for Zencart – here are some of the best of them:
Tons of free tutorials for the novice Zen Cart user.
Practical guides to increasing e-commerce sales.
Zen Cart tips as well as some very useful general ecommerce marketing and seo tips.
Apart from a massive portfolio of Zen Cart add-ons, That Software Guy has a wealth of tips and tricks
Views, ideas and tips for e-commerce developers and online store owners from the founder of Kuroi, specialists in Zen Cart.