Icons 8 is a regularly updated set of beautiful icons that are inspired from the Windows 8 interface.
Currently, there are 140+ items where 3 new ones are added each day (users can send suggestions for new icons).
They are in transparent PNG format with 26*26px size and come in black&white colors.
There are icons of arrows, e-commerce, payment methods, sports, music and more their community voted for.
Website: http://icons8.com/
Download: http://icons8.com/download-huge-windows8-set/
Vote: https://icons8.uservoice.com/