Here are some of the resources I use daily and also recommend.
WordPress - the CMS that this site runs on.
Genesis theme framework - WordPress theme framework with lots of beautiful themes.
_s starter theme - WordPress starter theme used by the Automattic theme team.
WooCommerce - E-commerce plugin for WordPress
Fail Harder – Before diving into e-commerce, read this stuff and buy the books
Kalzumeus - Patrick McKenzie on smart promotion