If you're unfamiliar with GRC Expert, our publication covering SAP compliance and risk management topics, as well as sustainability, enterprise performance management, and some security, a good resource is a post I put up at the beginning of the year.
I linked to the ten most popular articles among our readers from 2009. The articles cover a wide range of functionalities, from pieces of SAP BusinessObjects Access Control to standard audit reports in your SAP system, and are written by both some of the top experts inside of SAP and most knowledgeable consultants.
If you're not a subscriber, you'll be able to read the abstract and introduction to get a feel for what the article is about. This applies to all articles in the knowledgebase, so I encourage you to search or browse by category to see what else we have.