How to tell which w3wp.exe worker process belongs to what Microsoft IIS application pool

Have you ever had an IIS worker process (w3wp.exe) that was taking up a lot of memory and wanted to know exactly which application pool it was tied to? 

Run this script located at C:\WINDOWS\system32 from command prompt:

cscript iisapp.vbs

This will tell you you the process ID of each worker process as well as the application pool ID it is running under.  This can help troubleshoot exactly which website or application is causing the memory spike.