Love this site http://thenounproject.com/ - an open collection of user generated icons and symbols that are downloadable, free, useful and generally rather good.
The Noun Project Mission
“sharing, celebrating and enhancing the world's visual language”
The Noun Project collects, organizes and adds to the highly recognizable symbols that form the world's visual language, so they may share them in a fun and meaningful way.
The symbols on the site are and always will remain free. They believe symbols can not be effectively shared with the world if they are not free.
Everyone likes simplicity. They want you to be able to come to their site and effortlessly find and obtain what they're are looking for. Simple as that.
They think a language that can be understood by all cultures and people is a pretty amazing thing. They also think their symbols and the objects or ideas they represent are works of art worth celebrating.
They get excited about things like scale, proportion, and shape. They are committed to design and quality in everything they do.
Found via http://www.presentandcorrect.com/blog/