An interesting one is Glover Island in Grand Lake, the largest lake in Newfoundland. Remote and uninhabited, it's 24.2 miles long and 3.2 miles wide. Glover Island contains a number of ponds and lakes, and the largest contain islands themselves. Each of these has the distinction of being an island in a lake on an island in a lake on an island.
http://en.wikipedia.org/wiki/Glover_Island
http://www.kayakers.nf.ca/sea_kayaki...overisland.jpg