Nationwide Lifts - Engineering Games - Thanks Kira for sending this great resource!  I love how the games and simulations teach you through play and challenges.

Enriching Mathematics

Science and Technology of World War II - The National WWII museum present lessons, acitivities and information about the Science and Technology used in WWII. They do have a Virtual Fieldtrip for $100.  Appropriate for Grades 7-12.

Kids Ahead - Explore Wind Energy, Video Games, Robotics, Extreme Weather, and Crime Scene Invesstigation. Elementary

STEM Works - Articles, activities, cool jobs, subjects, locations and events about STEM

STEM Resources - Developed for Tennessee standards.  It has STEM Education Apps and other resources.  It also has some suggested Virtual Fieldtrips and a Powerpoint the describes what to do before a virtual fieldtrip.  It is filled with teacher self-assessments.