This link is a superb jumping off point for a range of icons and pictograms. Sometimes finding quality, versatile icons is pretty hard, and designing your own can rapidly turn into a nightmare. These all can be used as is, or endlesly modified to become an ever expanding toolbox.
In the words of Meagan Fisher from Brooklyn who did the roundup:
I can’t overstate the value of a good flat, sharp, detailed icon. You can style it any way you please, use it in a variety of projects, and communicate difficult interface concepts in a 16 pixel space. Considering the incredible amount of work that goes into designing each icon, and the quality exhibited below, these sets are scandalously low priced. So get ready to do some serious tax-deductible shopping.
Check them out here…