Physics & Maths Tutor (PMT) is a free resource aggregator with worksheets, notes, and past papers for A-Level and GCSE science and maths subjects.
PMT is excellent as a free supplement for past papers, but its IAL Maths notes are inconsistent and text-heavy. Mathmap gives you a complete, accurate, visually-structured revision guide for all six IAL Maths modules — built by an active IAL Maths teacher.
The first chapter of every module is completely free — no account, no payment. See for yourself.