Crash course on psychology
This series of YouTube videos can be useful e.g. for reviewing

Why an entire field of psychology is in trouble?
SciShow video on the replication crisis in psychology. This is video is also good for reviewing content related to the approaches to researching behaviour.

Internal validity tutorial
Two part Athabasca university tutorial on the topic

Pearson correlation coeffecient calculator
You can easily calculate correlations with the help of this website

Correlation does not imply causation, or does it?
MinutePhysics video on the topic

Qualitative research methodology
A quick overview of qualitative research methodology by Dr Dee

Why most personality tests are wrong
BrainCraft video on the topic

IBO's ethical guidelines for IA-task
Are the IBO guidelines in line with general ethical guidelines from other sources?

APA's ethical principles
How different or similar are these codes in comparison to other sources?

BPS's code of ethics and conduct
How different or similar are these codes in comparison to other sources?