Here below some useful links, divided by categories:
DESIGN & ILLUSTRATION
https://www.canva.com/
COLOR GRADING
https://coloristsociety.com
https://www.shopfsi.eu
https://www.colorgradingcentral.com
https://mixinglight.com
COLOR SITES
https://color.adobe.com/it/create
https://colorhunt.co
https://brandcolors.net
https://uigradients.com/#Mirage
FONTS SITES
https://fonts.google.com
https://www.fontsquirrel.com
https://www.dafont.com
https://www.myfonts.com
LEARNING
https://thefutur.com
SCRIPTWRITING
https://boords.com/storyboard-creator
https://www.fadeinpro.com
MOCKUPS
https://www.ls.graphics
https://graphicburger.com
https://smartmockups.com
https://themockup.club
ONLINE MARKET
https://creativemarket.com
https://elements.envato.com
https://www.designcuts.com
MATTE PAINTINGS
https://www.jotform.com/blog/40-matte-painting-masterpieces/
VIDEOMAKING
https://www.blackmagicdesign.com
GOOD HARDWARE
http://www.flandersscientific.com
FRIENDS
https://www.robertopanucci.it
https://toskyrecords.com
COMMUNITY
https://www.lynda.com
https://www.behance.net
https://dribble.com