Can anybody provide samples/links/simple-illustrations/videos/demos on how to use the messenger class in MVVM Light?
You should look into the source code of MVVM Light on CodePlex: http://mvvmlight.codeplex.com/SourceControl/changeset/view/47157
If you look into the samples, you will see that the CleanShutdown example uses the Messenger class.
In the IssueVision.SL example application, the messenger pattern is used to catch menu clicks and let the mainpage switch the views.
Blog of Laurent Bugnion (GalaSoft)
MVVM light - how to access property in other view model on stackoverflow