Check out your local architecture - take a walk around town to spot some of the best buildings. See if you can find out when they were built, or who the architect was.
Most 'town' brochures or postcards feature photos of the 'best' parts of town, or areas of natual beauty. Take a hike around and try to spot 'views'. Why not see if you can replicate those photographs yourselves. Where exactly did the photographer need to be standing in order to take it?
Take an audio tour using your MP3 players There are several free audio tours available for download. Do a search for 'audio tours' for your area, or see what is available from Tourcaster
Visit your local tourist information office to collect brochures - and quiz the staff about your town. It is interesting for the children to meet people who are knowledgeable about the geography of the area.
Is there a big industry near you? Watch aeroplanes land, or delivery vans leaving the factory. Find out who the top three producers are in your area and compare their location and premises.
Go look at your local wind turbines or other power plants
Make a tour of your local bridges, or other engineering feats.
I hope these ideas for geography field trips get you started! For more ideas, why not check out these Free Field Trips.