Diffen is a nice resource for those times when you need a quick comparison of two things. Let's say you need a chart to highlight the differences between latitude and longitude, Diffen has that. Or perhaps you need a comparison of Medicare and Medicaid, Diffen has that too.
If you can't find the comparison that you need, you can create your own on Diffen. Diffen is a community site. Anyone who registers on Diffen can contribute to the comparisons on the site. Comparisons are not limited to text. Images can be added to the comparison charts on Diffen. An embed code is available for each chart. I've embedded the comparison of latitude and longitude below.
Applications for Education
Diffen could be a good place to find comparisons to post as references on your classroom blog or website. The latitude vs. longitude chart and the homonym vs. homophone chart are two that jump out as good options for classroom blogs.