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.

