This script will crawl through a SharePoint Web Application and put out all the site collections and library where InfoPath is found, specifically the site owner, the site URL and the library URL.
Within the foreach, the script checks if there is a base template "XMLForm" used or if InfoPath is enabled.
Oh! And of course you will get a .txt at the end, remove the header and the footer and use it in Excel or in a SharePoint list!
Matthew McDermott wrote a similar script before I did.