Flaticon - A database of free vector icons.
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.
Freepik - More than a million free vectors, PSD, photos and free icons. Exclusive freebies and all graphic resources that you need for your projects
Icons8 - Free app for Mac & Windows already containing 39,800 icons. Allows to search and import icons…
Nucleo - Commercial vector icons and accompanying apps to manage and customize them.