Benjamin Reid is sharing a set of 81 social bookmarking icons named Social Media Bookmark Icon + where it is possible to find almost every social network.
The "+" in the name refers to the continuous additions being made to the set upon user requests.

They come in 3 different sizes:

  • 16*16px
  • 32*32px
  • 122*42px (large buttons)
And, all icons are in PNG format.