Flaticon - A database of free vector icons.
Freepik - More than a million free vectors, PSD, photos and free icons. Exclusive freebies and all graphic resources that you need for your projects
Font Awesome - Font Awesome makes it easy to add vector icons and social logos to your website. And version 5 is redesigned and built from the ground up!
The Noun Project - Creating, Sharing and Celebrating the World's Visual Language
IconArchive - Search through more than 735,000 free icons. Browse icons by category, artist, popularity, date. Organize and share your favorites.
Streamline icons - The world’s largest icon pack library - 100k icons and illustrations.