Of particular interest is the Kerningjs library which combines the previously available letteringjs library. What these libraries do is to make each glyph (letter/number) into its own element each of which can then be transformed by CSS like rules. In plain speak, these code libraries allow you to change each letter individually in a paragraph or heading etc.
There are some nice demonstrations online about why this is interesting, the most interesting demo can be found at kernjs. Try visiting that page, double click the big blue circle then click on and drag the letters individually.
If you then click ‘Finish Editing’ you will get the CSS controls necessary to implement this effect (if you had kerning.js linked from your page).
There is also another interesting typographical library called colorfont which enables dual toned glyphs.
It is a pretty good trick they used to achieve this. Essentially they created two fonts from the same master font each displaying just partial glyphs. When overlayed they display the full glyph. Hence each ‘layer’ can be targeted with a different color.