If you're using SIMILE's Piggy Bank Firefox extension, you'll find lots of juicy RDF data to work with in HubMed.
It doesn't work so well on pages of search results (search.cgi) as it insists on importing the linked Atom and RSS feeds as well, so you end up with everything three times.
However, it does work very well on abstract display pages (display.cgi) - just click the little data-coin icon that shows up in Firefox's status bar when linked data is available.