Classy icons crafted according to Microsoft guidelines. Available in PNG and SVG. Free for a link
Feather Icons - Simply beautiful open source icons
Direction Local - Quickly Boost Your Local Search Rankings
IconStore - Free icon packs by first-class designers
DemandSphere - DemandSphere is an advanced-level software that helps marketers to create the best digital appearances of their brands.
Flat Icons - 20,000 unique, customizable icons with free lifetime updates
Searchmetrics Suite - SEO Software