Okay, it's not REALLY social media, but it is web-related and good for authors to know for their own website. Top 10 Fonts Web Designers Love [Infographic] (good free font list)
10 Great Web Font Combinations for Your Resume
Great ideas here in the 10 Commandments of Typography for designing future resumes.
Grammar Rules of Graphic Design
Typeface Rules of Graphic Design
Spacing Rules of Graphic Design..things every designer should know!
15 Golden Principles of Visual Hierarchy | http://www.designmantic.com/blog/infographics/15-golden-principles-of-visual-hierarchy/