Listed below are a few electronic sources on Thanksgiving:
Sweetsearch Webguides: http://www.findingdulcinea.com/guides/Entertainment/Holidays/Thanksgiving.html
Thanksgiving History: Plimouth Plantation: http://www.plimoth.org/learn/MRL/read/thanksgiving-history
History of Thanksgiving from History.com: http://www.history.com/topics/thanksgiving/history-of-thanksgiving
First Thanksgiving from National Geographic: http://kids.nationalgeographic.com/content/kids/en_US/explore/history/first-thanksgiving/
Primary Source Sets from Library of Congress: http://www.loc.gov/teachers/classroommaterials/primarysourcesets/thanksgiving/