http://az12722.vo.msecnd.net/vs2010trainingcourse2-1/labs/introtomef1-1-0/Source.zip

Isn't that it? There are 3 exercises in it. I haven't used it, but it is the third link on the page:

http://msdn.microsoft.com/en-us/VS2010TrainingCourse_IntroToMEF

and

http://msdn.microsoft.com/en-us/vs2010trainingcourse_introtomef_topic2