A nice outline of metadata in HTML including SHOE, microformats, eRDF, and RDFa in the context of searching based on annotated Web content is available at ReadWriteWeb: Making the Web Searchable: The Story of SearchMonkey by Alex Iskold.
David Peterson gives a good analysis of what Yahoo’s announcement means for sites wanting to get semantic information into search results.
On Bob DuCharme’s blog, an interesting perspective from Sarah Bourne, the Chief Technology Strategist for the Commonwealth of Massachusetts:
If Massachusetts pursues enriching our content, RDFa seems a more likely candidate. We prefer to adopt things that have been created and promulgated by standards bodies: they are more stable, the deliberative process surfaces and resolves problems beforehand, and are the only reliable basis for interoperability.
Bob DuCharme has posted an excellent analysis of the value of RDFa and how it compares to microformats.
So, congrats to Leo and Richard: Cool URIs for the Semantic Web is a W3C Working Draft, now. They basically discuss URI design issue regarding both humans and machines. Why do we care? Well, let’s have a look into the document:
The solutions described in the following apply to deployment scenarios in which the RDF data and the HTML data is served separately, such as a standalone RDF/XML document along with an HTML document. The metadata can also be embedded in HTML, using technologies such as RDFa [...], microformats and other documents to which the GRDDL [...] mechanisms can be applied. In those cases the RDF data is extracted from the returned HTML document.
What is your opinion? Do you have practical experiences — that is: no toy setup 
— in designing URIs in an XHTML+RDFa environment?
As Danny reported, it seems that Joost has triggered a race for using RDF in video metadata: ZDNet has reviewed the alpha version of Seesmic, an online video applications using RDF “as the foundation”, supporting vocabularies such as FOAF, SIOC, DC, MPEG-7 (cf. Multimedia Vocabularies on the Semantic Web report for further details). As an aside: Seesmic supports RDFa!
Benjamin Nowack has updated his comparison of RDFa to other metadata embedding techniques. Benjamin states that
… pretending to be constructive, and in order to make things less biased, I embedded a dynamic page item that allows you to create your own, tailored comparison.
WWW2006 is barely over, and folks are writing about RDFa. This is great news. The enthusiasm and inevitable questions and concerns are very encouraging, and we hope to address these as quickly as we can.
Check out Benjamin Nowack’s careful comparison of RDFa to other metadata embedding techniques. The one downside he points out: RDFa does not currently validate in XHTML 1.0. That’s true, but we had no other choice to achieve the features we need:
But fear not: RDFa does not break anything in today’s browsers. Not even in XHTML strict rendering mode. That’s a big deal, and it means that our upcoming effort to standardize RDFa for XHTML1 is going to be fairly straight-forward.
One significant advantage of RDFa: you can express metadata about other documents (embedded images) and about fragments of the document (a blockquote). And another significant advantage: you can aggregate content from multiple sources, and the metadata schemas will not conflict, thanks to XML namespaces.
Meanwhile, Evan Prodromou compares RDFa to Microformats. He seems worried that the disagreements will be problematic. We don’t think so. Microformats are useful for expressing a few, common, well-defined vocabularies. RDFa is useful for letting publishers mix and match any vocabularies they choose. Both are useful.
And since RDFa is more generic than Microformats, we have a proposal for transforming Microformats to RDFa. We’re still debating this, but it’s very promising. In fact, our calendar bookmarklet uses this technique to read both iCal RDFa, and the hCal microformat.