Using the experimental license choosers at CC Labs you can provide some optional information about your work, including a URL to be used for attribution and a URL where rights beyond the scope of the public Creative Commons license may be obtained.
If you provide any optional information it will be included in the license notice HTML generated for your site. The optional information will also be annotated so that a computer may discern, e.g., the URL you want used for attribution purposes.
The HTML rendered in the box above includes metadata. Click on the license button and the license deed will update itself to display metadata scraped from this page after a few moments.
If you're using Firefox or Safari (patches welcome for IE), you can see the metadata revealed without leaving this page by clicking this RDFa bookmarklet link (right click to bookmark the link and use on other pages).
MozCC (also for Firefox) can also reveal this metadata.
Note that the bookmarklet above reveals that text and links intended for human use are annotated directly. This is a big improvement over our use of RDF/XML embedded in HTML comments for extra metadata, which is hard for both humans and computers to see and understand.
Colocation of metadata and viewable content is accomplished above with RDFa, which uses attributes to annotate HTML elements.
There are some obstacles to RDFa adoption (it uses attributes that do not validate in current versions of [X]HTML) and microformats have lots of momentum, so we're also exploring a microformat or microformats for work information and other annotations that complement CC licensing. (But RDFa was easier to get up and running for this demo because we didn't need to write a parser.)
One of the strengths of the microformats process is an emphasis on documenting use cases in the wild before attempting to standardize. We've begun doing just this on a licensing examples page on the microformats wiki, which is an excellent place to get a feel for the range of uses that could be enhanced by metadata in the near future.
There are a few early experimenters publishing extended metadata that will work in the same fashion as the artificial demo above. Visit any of these, click on a CC license button, and see how the metadata is added to the CC license deed.
Jamendo is a "is a new model for artists to promote, publish, and be paid for their music." Nearly 2000 albums are streamable, downloadable via P2P, and many may be purchased via artists' sites, for example, Revolution Void's Increase the Dosage.
Scoopt makes it easy to sell your pictures and blog content to the press. Like Pump Audio, they offer a CC license option when a user gets a button for commercial licensing (press). One of the first blogs to get a Scoopt button with metadata that works with this demo is Kitchen Linker.