Well one no longer needs a top secret clearance to do just that. Several layers for Google Earth allow one to view imagery of some of Iran's nuclear sites and see the change over time. The three best layers (that I have found so far) include a 2006 layer of some locations (KML), and a 2007 layer (KML). A third layer shows the spot of underground buildings (KML).
A way to find more locations is via the Google Earth Community. Today there are hundreds if not thousands of amateur imagery analysis freely sharing information and resources with one another. A brave new future for the public and the intelligence community lies with easily accessed and shared knowledge.