Classy icons crafted according to Microsoft guidelines. Available in PNG and SVG. Free for a link
Feather Icons - Simply beautiful open source icons
IconStore - Free icon packs by first-class designers
Flat Icons - 20,000 unique, customizable icons with free lifetime updates
Streamline icons - The world’s largest icon pack library - 100k icons and illustrations.
Heroicons - Beautiful, free SVG icons from the makers of Tailwind CSS.
Tabler Icons - 550+ free fully customizable SVG icons