not sure about the non-STEM subjects, but for hands-on projects in the STEM area, I would really recommend the SMILE project, a listing of hands-on activities for different STEM subjects.http://howtosmile.org/
Khan academy is also a wonderful resource for math and related subjects (https://www.khanacademy.org/
There's also a ton of resources from museums around the US, such as the smithsonian museum: http://smithsonianeducation.org/
If you're looking at engineering, definitely check out instructables projects -- for electronics, for instance, I'd recommend something like "blink an LED", everyone tends to like shiny things (http://instructables.com/
And of course near and dear to my heart as an MIT alum there is the MIT OpenCourseWare high school resources page: http://ocw.mit.edu/high-school/index.htm
I made a longer post here:
Good luck! I realize this thread is old but if anyone has any questions feel free to PM me.