It just hit me that it's extremely annoying to manage bookmarks, and I REALLY want people to stick more metadata in their document headers, and for bookmark managers to extract it and annotate the bookmarks and let me use the data to search the stored bookmarks. It's one of those blindingly obvious uses of RDF/RDF-A, and one where Dublin Core entities are already widely used for Search Engine Optimisation purposes so a lot of data is already in there, some of it in a form that fits exactly or almost with RDF-A.
Couple it with other RDF data sources available for webpages, such as RSS feeds and Open Directory, and you could get quite good coverage.
The upside of marking up your static content this way is that it would make it trivial to put together a program to scan your site and generate an RSS file of all recently changed pages as an added value for your regular users.