Another source of information might be the Performance Database (transaction ST03 and STAD).
A good alternative is security and audit logging. Security and audit logging keeps track of all programs and transactions in use. It offers a search engine to look for specific reports, transactions and users. The security portal in the SAP service marketplace (http://service.sap.com/security) contains much more information on how to setup security logging.
This was first published in July 2006