"Open Clip Art Library" that can obtain over 6900 free clip art

You can download various clip art licensed in public domain, Creative Commons.

There are also many icon-like things that can be used in site creation, presentation and reporting, so it is useful when you want to add a bit of accent.

Download from below.
Open Clip Art Library :: openclipart.org :: Drawing Together.
http://www.openclipart.org/

You can search by searching "Clip Art Search by Keyword BETA" on the above page.

From here if you want to search by genre
http://www.openclipart.org/cgi-bin/navigate

From here if you want to download all at once
http://www.openclipart.org/downloads/index.php

The clip art available on this site is SVG format, so if you want to convert it to an arbitrary size and use it, it is easy to use the software described on the following page.

GIGAZINE - Free software that handles vector images like Illustrator "Inkscape"