Microsoft software on computers
This simple report lists all of the Microsoft applications installed on managed computers and how many computers have the software. It defaults to sorting in descending order of the number of computers with the software, but the report has "interactive sorting" enabled so you can sort within the report by the number of devices or by the name of the application.
You can change the SQL in the report so that it looks at other vendors (instead of Microsoft) and create similar reports.
The report is attached. Instructions for importing it are found here: Instructions for importing new reports