This site has units and lesson plans on: Lewis and Clark preparing for the trip, politics, mapping, women, animals, language, trade and property, plants. There is a section on exploring and using primary and secondary sources.
This is an amazing resource from the MAGE center at Macalester. Click on each of the sessions at the top to see a list of free curriculum resources on Social Studies themes. Also look for opportunities to do free education forums with this group. Very useful materials!
This website has information on Past population growth and future population growth. Students can find out what forces are responsible for the world's human population. Students can learn from models of future human population growth.
There is a ton of info on the records of Japanese-Americans on this cite. Just the map of the locations of the 10 camps is worth a trip to this source.