ZenCart is one of the most popular open source PHP ecommerce packages on the planet. Their documentation section contains contains hundreds of FAQs, tutorials and howtos. They cover everything from installation (32 documents as of this writing), templating and customization (52), general administration (48), order processing (6), security (8) and troubleshooting (32).
Link: http://tutorials.zen-cart.com/index.php
Popularity: 78%
