Microsoft Office has an entire site dedicated to clipart and it is free to use (okay you need to read the EULA - End User License Agreement for the fine print) but essentially it is free and there are truckloads of it. So if you are graphically challenged like me... not allowed out in public with coloured pencils or crayons, then clip art is for you.
Tom Khulman has blogged about his favourite styles in Microsoft's clipart and to be honest I had forgottten about them... a quick trip to bing, alright it was Google revealed the description.

First of all you can get to clipart from Word,PowerPoint, Publisher - come to think of it every office application you probably use frequently. You can also go directly to the website by visiting
http://office.microsoft.com/en-au/images/
You can select a category and then select by keyword or look for similar images.
In Tom's blog he says you can right click on a graphic to reveal the style number. If you decide to trawl through the library, be aware that third party providers are now contributing to this massive image library and they don't apply a style number to their images.
However, searching by style, if you know the style will work and as Tom suggests, putting in a random number can yield interesting results as well.
The url string to use to search for a style is http://office.microsoft.com/en-us/images/results.aspx?qu=Style 1190
Check out Tom's blog entry for even more style numbers. http://www.articulate.com/rapid-elearning/15-interesting-clip-art-styles-for-your-e-learning-courses/
where you enter your required style number instead of 1190 and the Office Clip Art and Media Web site shows clips in all categories that are similar in style to the number you enter. this allows you to add consistency to a publication, presentation or piece of eLearning by choosing clips that all have the same style number.
Note When you download clips from the Office Clip Art and Media Web site, you can no longer see the style numbers in Properties.
To see the style number for a clip (if one exists), click the clip on the Office Clip Art and Media Web site, and then view the Properties that appear.
