Steve Cayzer at the HP Labs has a Semantic Blogging demonstrator, taking advantage of the options for adding semantics to a weblog.
The only addition to the standard blosjom output used so far is RDF information for each individual post, which I should add to blaxm! at some point. The future expected modules are said to include a metadata assisted import tool, schema driven metadata editing facility, metadata based customisable blog views, semantic navigation and community queries.
There are three newsfeeds: RSS1, RSS2 and RDF. Although the RDF version contains the most information (such as trackbacks), I still prefer the RSS2 version as it's much easier to read and understand. Extending the RSS2 feed with modules to provide the same information as the RDF feed would seem to be the ideal solution. I think I'll add ENT information to the HubMed feeds in the next few days.