The Hacker Shelf is a “community-curated collection of free books” with a primary focus on technical, programming topics. I’d recommend a bookmark of this one, could be handy.
This is one of my favorite resources for writing a WordPress plugin. In his post, Francis Yaconiello, provides a great overview of how to setup a plugin in a logical fashion without over complicating things.
I’ve noticed that a bunch of the how-to-write-a-plugin articles out there focus on demonstrating the minimum amount of code needed to get a plugin going. Not many focus on good plugin structure or convention. This tutorial explains how to create a class based WordPress plugin that makes sense.
This site is a technical reference for various things including OSX, WordPress, SEO, Web Hosting, CSS and other tech like gems – the site is for my reference and yours – there is nothing like finding the right solution that works. ~ coolestguidesontheplanet.com