Are you bored of the Clip Art available from Microsoft Office? Occasionally, we stumble upon those few images that we have used repeatedly and just want some fresh art to insert into our PowerPoint presentations.
Open Clip Art  allows you to use their images for free unlike many other Clip Art websites. You will get some really unique images that can add zing to any project you are working on. The website’s aim is to create a kind of ‘Wikipedia’ of graphics. Since images are uploaded by people who have worked on it themselves, they do not expect anything in return.
You can still contribute and thank people for being able to use their images. One way is to submit your own images for others to use. The second is to report a problem with any technical issues, since they are still testing and developing the site. The third is to join discussions, so people can get feedback on their art.
~Zahid H Javali