Google Hangouts can be used for virtual field trips through Google's "Connected Classrooms" project. This connects classrooms with people and places all over the world.
Google describes it as follows: "Virtual Field Trips connects cultural institutions like museums, zoos and aquariums with schools and non-profits around the country via Google+ Hangouts On Air. Hangouts On Air allow institutions to share universal access to unique cultural and educational experiences regardless of geographical and financial restrictions."
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