Really Good UX - A library of screenshots for UX inspiration
Usability.gov - Resource for user experience (UX) best practices & guides
Laws of UX - Key maxims that designers must consider when building UX
UX Check - Easy heuristic evaluations on your website (chrome ext.)
UX Timeline - See how some of today's best companies have evolved
Heurix.io - Heurix is a free heuristic evaluation tool that helps you work out how to improve your website.