Teachit Maths specialises in Maths from 11-18, the growing KS5 collection which includes high quality resources can be found here. In April 2011 Teachit Maths became part of the AQA family with the aim of supporting teachers and learners to realise their potential. Teachit Maths remains editorially independent and is committed to publishing high quality resources, regardless of awarding body.
Teachit Maths has a particularly generous free subscription which gives you access to all the pdf files on the site (hundreds of them!). If you contribute resources to the site you gain benefits including a free subscription and royalties.
Teachit Maths – Investigating Quadratic Equations
Some further resources I particularly like are Integrating Trigonometric Functions, and Matching Graph Sketches a resource which mainly tackles exponentials and natural logarithms but includes a quadratic and a cubic example.
All Key Stage 5 resources.