These are great, and I once considered "how would you use data _null_?" as an hiring question to test SAS proficiency.

I use _NULL_ to call a web service that emails me a notification that my long-running SAS program is done. It's just four, short lines of SAS code that passes the name of the program to a special URL. While the functionality is limited, it avoids the hassles associated with MAPI/SMTP.