WooCommerce - A freely available eCommerce plugin that enables shop facilities on your WordPress website. Functionality enabling extensions & beautiful themes available.
UI Movement - The best UI design inspiration, daily
OpenCart - A free shopping cart system. OpenCart is an open source PHP-based online e-commerce solution.s
UI8 - Carefully crafted UI design assets
Jumpseller - Start Your Online Store! Grow your business.
UI Garage - Specific mobile and web design patterns for your inspiration