The Standards Unit is an outstanding resource with many excellent activities here for the secondary classroom including some for A Level Students – see Mostly Calculus. Start by reading Improving Learning in Mathematics – Malcolm Swan. This discusses effective teaching so well and should make you think about just what makes a quality resource for learning.
The resources are hosted by Nottingham University, including all the pdf files very clearly indexed. Note that this sites includes the complete set of resources including the software; (though some software is too old to work!) Note that Tom Button has rewritten the Traffic Simulations in GeoGebra for A5: Interpreting Distance-Time Graphs with a Computer. The Professional Development resources are excellent. Look at PD1 ‘Getting Started’ for example, note PD1.4 on page 9 – 8 Principles for Effective Teaching.