The Great Lakes and the vessels (Lakers) are not availeble for download for SS2006.
And they are not availeble for SS2008, however, SS2008 has the possibility to add ships afterwords.
As you, KEB1, i would like to see the Great Lakes and the Lakers in the game as well, but it will take time, i geuss. I think, we will have to wait for a future release of ShipSimulator to get more area's and ships.
Just be patient!