All subjects
These three sites cover many, if not all, the course materials of most of the subjects.
Seneca:
BBC Bitesize:
SAM learning:

Subject specific sites
Maths
 Khan Academy:
 Hegarty Maths:
 Prodigy Maths:
ICT
 Scratch:
Science
 Kerboodle:
 Active Learn:
 Mystery Science:
Geography
 Geography Games:
History
 History Department  
 Revise History YouTube channel:
 Big History Project:

Design  & Technology

 Technologystudent

Additional Resources

Ted Ed

National Geographic Kids

Activities and quizzes for younger kids.
The Kids Should See This

Wide range of cool educational videos
Crash Course

You Tube videos on many subjects
Crash Course Kids

As above for a younger audience
iDEA Awards

Digital enterprise award scheme you can complete online.
Tinkercad

All kinds of making.
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