portfolio sites

  Dribbble:
https://dribbble.com/

 Twitter
https://twitter.com/

 Insta
https://www.instagram.com/

 Pinterest
https://www.pinterest.com/

  Behance
https://www.behance.net/

 Tumblr
https://www.tumblr.com/

 Slideshare
(not a portfolio site, but you can upload slides and use them as portfolio pieces in LinkedIn)
https://www.slideshare.net/

 Pixiv: (illustrators)
https://www.pixiv.net/en/

 ArtStation (illustrators)
https://www.artstation.com

 Deviant Art (illustrators)
https://www.deviantart.com/

 Github (git) (coders)
https://github.com/

 Stackoverflow (stack) (coders)
https://stackoverflow.com/

 Coroflot
https://www.coroflot.com/

 Working-not-Working
https://workingnotworking.com