User A.I.Brown of ganfyd has been working on a HubMed extension for MediaWiki, which allows users to add tags like <hubmed>Myocardial Infarction</hubmed> that gets rewritten to add a link to a HubMed search for the specified keywords. There are options to limit the search to particular types of clinical queries and to build custom queries.
Ganfyd is a "free medical knowledge base [wiki] that anyone can read and any registered medical practitioner may edit".