Articles on medpedia have got a 'plain english' version, as well as a 'clinical version'. Only medical professionals can edit (after approval), but others can suggest changes. It's fun to compare a random article http://wiki.medpedia.com/Abacavir with the wikipedia equivalent: http://en.wikipedia.org/wiki/Abacavir.
There are departments at some organisations working in affiliation with Medpedia, including departments at Harvard, Stanford, Michigan, UC Berkeley.
Projects like this are obviously important to open up and share such knowledge, and make it all the more important to make mediawiki as accessible as possible.