The Open Clip Art Library (OCAL) is the largest collaborative community that creates, shares and remixes clipart. All clipart is released to the public domain and may be used in any project for free with no restrictions.
Joyce Valenza has created this wikispace list of all manner of copyright free searches and portals. As well as images and music their are pages related to avatar makers, concept mapping and clipart.
"IconArchive is a professional tag based icon search engine with more than 330,000 icons for web developers, end users and graphic artists. Also it is an inspiration source for new design ideas and a place to enjoy beautiful icons. You can collect, organize & share your favorite icons here with ease. If you want to customize your desktop, you can download icons for all operating systems, Win, Mac & Linux. Website or Software developers with demand for custom icon design could search for professional icon artists here. This may result in freelance jobs and/or design help for projects of any size. On our icon artists page you can select artists offering custom icon design."