RSC resource about chemical processes, includes video clips.
RSC site with lots of links to resources.
Lots of resources from the RSC for new chemistry GCSEs – demos, practicals, how science works etc.
Earth science resources – rocks etc.
US site, lots of lesson plans, activities and resources on chemistry topics for KS3 or GCSE.
Teach It Science is a subscription resources site, however if you register you can access all the pdf files free of charge, there are worksheets here for many topics at KS3 and KS4 for all three sciences.