Given schema.org's vague processing rules and general sloppiness with meta values, it's possible we're headed for a scenario where processing schema.org data is almost like natural language processing. This means other parties (outside of schema) will have a hard time using the data, giving Google, et. al. a competitive advantage. Parallels are drawn between this sloppy spec and the early days of HTML, when other browsers had to reverse-engineer IE's methods of rendering.

HTML5 Micro-vocabularies pioneered by the search providers.

More work on "hcitation".

The Microformats guys trying to figure out what the heck to do with these competing approaches.

An in-progress discussion on a microformat for Citations.

Mark Pilgrim on Microdata.

Google-supported microformat and microdata vocabularies.

A good overview of the HTML5 approach, different vocabs, etc.

Web service for converting microformats to iCal, vCard, etc.

A microformats parser for Ruby.

Microformats.org strongly advises against namespacing for content.

Microformats transformer and validator.

"The semantic web is a machine for creating Syllogisms"

Open social networks via WordPress plugins

John Alsop suggests another option for extending the semantic capability of markup: attribute meta-semantics.

BBC drops the hCal microformat because of negative accessibility effects of abbr-datetime design pattern.

The w3c on semantically bridging the gap between what humans see and what computers see. Similar in concept to microformats, but on a lower level.

Excellent interview with Adrian Hovalty about the creation and direction of Everyblock.

A possible microformat for increasing the semantic meaning in image "float" classes. Instead of "img.left", "img.right", etc, he proposes "img.figure.figure-a", "img.figure.figure-b", etc.

Yet another sweet microformat to take advantage of, packaged up nicely in a GUI