The Board of Studies do an outstanding job of making past exams, examples, and notes from the marking centre available for students. However, they can tend be distributed across multiple pages on their website. This collection should make it easier for you to take advantage of the materials.
Additionally, the Board has an excellent multiple choice question generator from past HSC questions, and in addition you will find narrated answers to questions that exposes my thinking and approach in going through multiple choice questions.
Use the Multiplce choice generator for Economics made available by the Board of Studies.
The Board also publish an outstanding and cheap 2012 HSC Exam Economics Workbook available for $26.50 for purchase on their online store. Very highly recommended - either buy one, or ensure your school library purchases one.