User Inyerface - A painful illustration of bad UX
Interfacer - Collection of more than 200+ free design resources
Befront - Learn UX/UI design skills in practice with bite-sized tasks
Facebook Design Resources - A collection of free resources made by designers at Facebook
Frontend Mentor - Supercharge your front-end skills by building in a real-life workflow. Solve real-world HTML, CSS and JavaScript challenges whilst working to professional quality designs.
Freebiesbug - Collection of the best free web design resources.