Here is my collection of Mock-ups, Font, Icon and Colour Libraries, Stock Images and Icons I was able to collect over the years. I use them on a daily basis and they help me make my work more efficient and fun. All of these are free or have a freemium option. If you have a recommendation for any other I should add, please let me know.

Colour inspiration

Adobe Color

Coolors

ColorSpace

Color Hunt

ColorSpark

Picular

Grabient

Fonts Libraries

Adobe Fonts

Google Fonts

Font Squirrel

DaFont

1001 Free Fonts

Stock Images

Unsplash

Pexels

Burst

Pixabay

Icons

Flaticon

Iconfinder

Noun Project

Mock-ups

Artboard Studio

Smartmockups

Mockupworld

Yellow Images