From Craig Barton, look at his latest site, DQaDay.

Really get your students thinking about these questions, not just answering them correctly but thinking about the questions you can see in the image – can you explain the mistakes and how can you be convincing that the incorrect responses are incorrect.

You can search for questions in various ways including the clear tags. Each question very usefully shows the spread of answers on Diagnostic Questions, a link to the question and a link to the quiz from which the question is taken. Check Labelling right-angles triangles for example.

Looking for questions by topic I really like the Collections.

There is extensive help available on Diagnostic Questions including these Help Videos.