Yucca on Characters
Want to read a treatise on the 18 different types of spaces in Unicode? How about on the 16 different types of hyphens and dashes (and their line-breaking properties)? OK, maybe you DON’T want to read about those topics, but need to? Try Jukka “Yucca” Korpela’s Characters and Encodings.
There’s lots more good stuff at his site, including this page of millions of useful links and tables related to web authoring.
(via dive into mark)