In addition to comparing the ozone hole from year to year, you may want to explore how it changes from month to month. You can return to the TOMS website and request images for every month of a single year. By converting the images to a stack and animating them, you can create a time-lapse movie showing how the hole changes through a year.
You might also choose to use the global format images (Global Image - TIFF (1280 x 960) available at the TOMS site to examine how the concentration of ozone changes in both the Northern and Southern Hemispheres through the year.
TOMS data is also available for the Northern Hemisphere. You can analyze this data to see if a hole appears in the spring in the Arctic.