Below is some useful links for the Advanced Higher course.
M4ths.com (A level notes but very useful)
Mr Timmons Maths (Lots of practice papers, past paper solutions, video solutions and lots more!)
West Lothian Maths (A useful site containing AH notes)
Advanced Higher Maths Revision (A useful revision tool for the course)
Algebraic Long Division (An online demo of algebraic division)
Matrix Transformation Practice (An online tool for practicing matrix transformation in a more visual way)
Knox Academy (A very useful website that has some good resources for revision and extra practice)