Code guide - Standards for developing flexible, durable and sustainable HTML and CSS written by @mdo.
CSS Linear, Radial and Repeating Gradients
Using gradients declared in CSS. Great article explaining why.
Article by Trent Walton about responsive design
The missing font generator
FontPrep is a font generator for TTF and OTF font files. It generates the font-formats for the web.
Cabel Sasser talk
Amazing talk by Cabel Sasser from Panic at the XOXO Festival (2013). Appreciating Coda 2 even more after his honest speech.
Getting started with pattern libraries
Excellent article in which Anna Debenham explains the work she did for the ALA pattern library.
She also gives a link to her own bookmarks for pattern libraries: Gimme Bar collection of pattern libraries
iOS 7 Colors
iOS 7 inspired colors and gradients reference site
Excellent style guide/pattern library reference Code For America.