Here are three neat interactive visuals to support teaching the periodic table. These could easily be used with 5th grade science all the way through high school.
The Interactive Periodic Table is, at first glance, a normal looking table, but click on any of the elements and you get a direct link to their Wikipedia entry, complete with at least one picture and lots of information.
The second is the Visual Elements Periodic Table. It's cool looking, but even better, when you click on an element you get information in a very basic, easy to read layout, along with a few more links to view some pictures and get more visual information. Extremely easy to use, great visuals, and the text is very accessible by lower level readers.
The last one is fun and will definitely have a "niche" appeal to certain students - this is the Comic Book Periodic Table. You click on an element and you will get a listing of what comics that element has appeared in. When you click on one of the issues, you get the full page from that comic so you can see the story line, and how the element was used - a great way to bring science fiction and imagination to the periodic table!