What started out as an internal project for Benedikt Lehnert eventually became a valuable typographic resource for writers all over the world. Making life easier for his fellow designers in their daily adventures with typography was the main reason for this custom-made "cheat sheet".
While typoguide will not replace an old fashioned and more complex book on the subject, it will certainly provide a lot of insight for those unfamiliar with certain typographic practices.
I like that it is light-weight, easy to navigate and straight to the point. A printed copy is also available.