Map applications

Open Street Map

• http://www.openstreetmap.org/
• Road maps with a layer optimised for cyclists.
• Footpaths are often shown.
• Aerial views but you have to be in "editing" mode.

Google Maps

• https://www.google.co.uk/maps/
• Road map
• Aerial views
• Street View (useful)

Google Earth

• This application needs to be installed
• Aerial views with or without roads, other transport options and many other features
• Street View (useful)
• Measuring tools
• Open and save track logs and push pins

Bing

• http://www.bing.com/mapspreview
• Road map
• Aerial views
• In the United Kingdom, Bing maps supports an Ordnance Survey view. This is really useful.