A fine idea and interpretation of HTML elements in the well known format of a periodic table is a nice find. Over at JoshDruck.com you can find just that. Displayed in a very clean and organized format and sorted and grouped by HTML element usage.
Making a good impression, the table gives a global view of the elements sorted by color into Root element, Text-level semantics, Forms, Tabular data, Metadata and scripting, Grouping content, Document sections and Interactive elements. Clicking on an element button opens a pop-up dialog which displays for what purpose the selected element can be used together with a direct link to W3 and Mozilla where you can find out more.
A really fine idea!