Resources by a science educator on topical news stories, for KS3 and KS4.
From National STEM centre, collections of useful resources for KS3 topics.
Matching puzzles for KS3 units, useful for revision.
Teach it Science is a subscription resources site, however if you register you can access PDF files free of charge, there are worksheets here for many topics in KS3 and KS4 for all three sciences.
Teacher website with various resources – particularly for respiration and circulation at KS3.
Thousands of words for science at KS3 with ideas for starters / plenaries – look in Free Resources for ideas.