A few I use regularly...
Montreal
http://www.navurb.com/nu_inter/Click the Orthophotos 2002 eyeball in the pane at right.
Pinellas County, FLA
http://pubgis.co.p....fl.us/public_gis/Click the camera icon in the toolbar. This one requires an Autodesk plugin.
Historical air photos of various Canadian places
http://airphotos.n...os101/images_e.php Satellite imagery for Canada
http://www.pfc.for...rces/images_e.html The resolution of that last one isn't as good as the air photo sites, but it gives you the option to download a 3.2 GB data set that covers all of Canada plus a goodly chunk of the northern US (free ER Viewer required). Pretty damned impressive!