When I wrote my recent article on Language Workbenches, I decided to separate the section on further reading into my bliki, to make it easier to report updates when new stuff appears.
For the last few years Intentional Software has been hiding under some deep rocks. They are beginning to peep out now. The main site for more on their work is http://www.intentsoft.com. In particular it's worth keeping an eye on their blog. Perhaps the best description of the Microsoft research is in chapter 11 of Czarnecki and Eisenecker.
JetBrains have an active community and I expect this will continue for their Meta Programming System. Sergey Dmitriev, the leader of MPS, wrote an excellent summary of his vision for MPS and Language Oriented Programming.
As one would expect from Microsoft there's plenty to find on Software Factories. The main page for information is on MSDN. It's also worth checking out various blogs: Steve Cook, Jack GreenfieldStuart Kent, Keith Short, and Alan Wills. Tracing through the Software Factory blogs will also give you some insights as to the debates over the use of MDA, since much of that discussion has been around the Microsoft work.
Speaking of MDA, there are a number of organizations trying to build something like a Language Workbench using OMG standards. I haven't looked into any of these in any detail. One such organization is Xactium.
My colleague Neal Ford has ported the initial example of the paper to Java and provided a download for the code.
Rainer Joswig discusses doing this in lisp and even has a video.
I intend to keep an eye on this field and expect to post further material on martinfowler.com.