I just came across this section while searching for the same issue. There is a German blog entry that describes an example of how to integrate Mondrian with Seam and Open Flash Chart.
The blog entry is in German (for non German readers maybe the Google translation is of some use), but you can also download the example seam project (all JAR files must be copied from the Seam distribution).
I'm also evaluating Mondrian currently if it is useful for a project where I'm just about to implement a truckload of statistics. In case it is, I'll use the idea from the blog entry and build the seam structures around it.