Okay, maybe it's not inherently the most educational site on the web, but what a neat way to create some great clipart that is personalized for your students or your classroom. This website http://txt2pic.com/ has a long menu of templates that when you click on them, you can add your own text or pictures to create personalized graphics for your websites, wikis, blogs, desktops, whatever.
I particularly liked this link where I made the etch a sketch picture, and this link with the Norman Rockwell poster. And this one is lots of fun for adding borders to pictures.
CAUTION: Not all of the links/images in the mega-list are appropriate for school. Please pay attention to the short descriptors next to each link, and as always with material on the Internet, preview before sharing with students.