PNG ICO ICNS MORE
Social media
Flat
Google +1 icons
plus, green, One
ForestGreen
256x256
google, One, green
Smooth
YOOicons Social Bookmarks
G+, plus one, plus
512x512
Desktop apps
Glyph
16x16 Free Toolbar Icons
create, green, adding
16x16
PNG MORE
UI
Pixel
Tiny icons
Add, plus
10x10
plus, Add, green
Mixed
3D
Flavour Extended
button, green, plus
48x48
Network & communications
Oxygen
plus, Add
Function icons