Buy 3 Step - Creative Corporate Business and Personal Portfolio Template by dixipixi on ThemeForest. 3 Step is a Clean and Modern Material Design Creative Template for Corporate Business, Corporate Portfolio, Cr.
Salesforce Lightning Design System. It's quite comprehensive: design philosophy, components, voice and etc. The home page provide quick link to tutorials and downloadable resource. A good ramp up for new user. Though everything here feels a bit generic. #designguide