Microsoft has made it easy to locate a view to use when creating a custom report. On TechNet, they have grouped the reports into to categories such as Inventory Views , Discovery Views, and Software Update views. Below are links to two key categories that I use regularly along with a link to all views.
Discovery Views - Use to find machines and users discovered by SCCM.
Inventory Views - Use to find installed software, hardware information, and files on machines.