These guys used to be on the Homepage but now they have their own page. Terraserver has black and white sat photos from uncle sam AND the russkies. Excellent navigation (even though Microsoft Sucks). Maptech used to do the NOAA charts & aerial photos but had weak navigation. Now its outside NOAA. Excellent products, color aerials and even free charts, you can even put your cursor over a spot to get the coordinates. You just have to deal with the popup ads (a small price to pay for an excellent product). Mapquest, also toggles between maps and aerials but while it has better road maps, it's not as good at sea.
But Google has revolutionized it all!
Check out Google Maps...switch between maps & aerials...Google Earth on your desktop...and...
For You Treo Junkies...
The ultimate handheld map download!
And Now....the latest addition... from the boys @ Maptech
Combining two (or three) of my favorite words...
Free & Boating Charts...
The name says it all!