This is a beautiful and free social media bookmark icon that designed by “nouveller” a member of deviantArt. I think it’s a good set of icons design.
In the zip file, you’ll get 3 sizes of all the popular social media sites icon such as Digg icon, Facebook icon, deviantART icon, StumbleUpon icon, redit icon, WordPress icon, blogger icon and more.
The buttons are available in 16*16, 32*32, 122*42 pixel in .png format. You can download and use wherever you like, for free as well!