To find free clip art images to use in Microsoft Office products, go to Bing.com, click on the Images option, then type what you are looking for in the Search field. Since you are interested in clip art images, be sure to include the words "clip art" to the search.
If the Microsoft Office suite you use is the 2007 version or a later version, you do not have to leave the document to go and search for images. Instead, click on Insert, and then click on Online Pictures. The clip art pane automatically directs to Bing.com.
Bing allows users to filter images by license type, limiting search results to images that are in the public domain and do not have copyright protection. To use this filter after running an image search at Bing.com, click the License drop-down menu, and then select a licensing option. Bing's filter selects the Creative Commons system by default, meaning that you can use, publish and redistribute the images without a copyright claim.
Another option for accessing clip art is to download it from a website that specializes in it, such as OpenClipArt.org. Search for what you want, download the image, and import it into your document.