I use these sites over and over and over again. Now they're all in one place (outside of my bookmarks bar). Add ones you like in the comments.
  1. The Noun Project
    https://thenounproject.com - beautiful vectors of every object or symbol you could imagine.
  2. Coolors
    https://coolors.com - dead simple color scheme generator. Tweak, save, and share your pallettes.
  3. CG Textures
    http://textures.com - great resource for hi-res, real world textures and seamless patterns.
  4. Behance
    http://behance.com - the best show room for other designers' work. a great place to go for inspiration.
  5. Font Squirrel
    http://fontsquirrel.com - thousands of free fonts, clearly tagged and searchable.
  6. All The Free Stock
    http://allthefreestock.com - awesome agregator of all the royalty free stock image sites out there.