to build up a community I think it would be nice to have a "DSLs zoo" like the one of other Language Workbenches (see for example http://www.eclipse.org/Xtext/community.html
I would offer to create a website and list different experiences, showcases, links to your blogs or websites and repositories.
In this way we could learn about similar efforts (possibly join forces), learn about best-practices, get the feeling of what the community is building.
Moreover having a list of projects using Mps could be useful for research reasons (I am a PhD in Language Engineering).
What do you think? Are you interested in participate?