http://www.field-trips.org/sci/oceank/index.htm - Oceans: Click on teacher resource link and then start the project link.
http://www.field-trips.org/sci/rainforest/index.htm - Rainforest: Click on teacher resource link and then start the project link.
http://www.field-trips.org/sci/sharks/index.htm - Sharks: Click on teacher resource link and then start the project link.
http://www.field-trips.org/sci/green/index.htm - Getting Green (Ecology): Click on teacher resource link and then start the project link.
http://www.eduplace.com/projects/index.html - This is Houghton Mifflin's project page. It has the four subjects broken into four buttons.
http://teacher.scholastic.com/maven/ - Interactive math games students can play online for basic skill reinforcement.
http://teacher.scholastic.com/immigrat/ - Immigration: Contains an interactive tour of Ellis Island.
http://teacher.scholastic.com/activities/explorer/oceanlife/index.htm - Ocean Life: work with Costa Rican Sea Turtles or New Zealand Dolphins.
http://teacher.scholastic.com/space/ - Space Frontier:
http://www.he.net/~sparker/cranes.html - Sadako: Cranes for Peace began as a project to collect paper cranes to be sent to Hiroshima for the 50th anniversary of the bombing. Also many other related links.