Iconic icons: Celebrating design’s nifty little helpers
Solid vs Outline » Welches Icon ist besser zu erkennen?
Hollow Icon vs. Solid Icon: Which Is More Friendly for Recognizing? | by Trista liu | Medium
Solid Vs. Outline Icons: Which Are Faster to Recognize?
Master's Paper | Filled-in vs. Outline Icons: The Impact of Icon Style on Usability
Solid vs. Outline Icons: Which Are Faster to Recognize?
Accessible Icon Buttons — Sara Soueidan – Freelance-Front-End UI/UX Developer
a11ySolid Vs. Outline Icons: Which Are Faster to Recognize?
Redesigning the Office App Icons to Embrace a New World of Work
Fontello
icon fonts generator
About those vector icons · Pushing Pixels
Apple OS X Lion Buttons in CSS
Freebies Booth
Free design resources layered PSD, resizable vectors, PNG icons
free ui set from medialoot
… and a preview of what’s to come