I've collected together a few lesson plans for teachers to use as a resource for their classes. Feel free to use these as you wish. I've tried to target these at secondary school level, but you may also want to check out the primary school ones too for more basic lesson plans and facts.
GENERAL
HISTORY
GEOGRAPHY
Basic physical and human geography of India including worksheets
Mountains, rivers, glaciers, lakes and geology of the Himalayas
Physical features of the Himalayas
Fold mountains and the Himalayas
MAPS
List of states, their capitals and a map
A range of maps of India including physical, political, railways, rivers, etc.
Incredible India - Facts and activities
RELIGION