Flat is still all the rage in website design, and flat icons are a huge part of this design aesthetic. One of the best selection of flat icons I have ever seen is IconShock’s Flat Icon set
IconShock offers different set’s of icons, grouped into really useful categories (like security, medical, or graphic), or you can buy a massive archive of all the flat icons – over 38,000 icons in total!
If you’re not into flat, there’s an amazing Material Design icon set, Outlined icon set and even a massive set of Mobile icons optimized to both iOS, Android and Windows 8 UI guidelines.
