One of the Lesson Planning series of pages is on Misconceptions, this has been updated recently to include examples of helpful material from the examination boards which address common misconceptions, such resources can promote very useful class discussion as can examiners’ reports.
See for example AQA’s Exploring Common Misunderstandings in GCSE Maths.
From Cambridge University, see Common Errors in Mathematics.
Edexcel’s A Level scheme of work which is freely available on their website includes for each section, Common misconceptions/examiner report quotes. The point made in the notes which follow is such an important comment, I have seen many errors that would have been avoided if only students had looked at a picture of their work.
In Mathematical Miscellany #77, I mentioned one of my go-to websites, Corbett Maths, I was interested to see that John Corbett has been adding some updates. I noted in that post 6 new Estimated Mean and 10 new Order of Operations questions, he has now updated Expanding two brackets and Substitution; video solutions are available for both.
From Tim Brzezinski, here’s a lovely collection of Open Middle themed problems where students build special quadrilaterals in the coordinate plane so vertices have no repeated coordinates.
On the subject of quadrilaterals, have a look at this new resource, a Measuring Shapes workbook from Curriculum for Wales.