Where are pictures of Earth?

NASA has 1000's of photos of Earth from space including those from Apollo, Gemini, and shuttle missions.

You can search/browse many such photos on web or order CD-ROMs for large collections of such images.

If you want to see high-resolution Earth-centric satellite or aerial imagery then Google Earth and Google Maps are great tools to view it.

Likewise, if you want to see high-resolution imagery of Mars or the Moon then Google Earth has that too including related mission details, routes, video clips, etc.