Looked it up (the joys of working in a library). The essay is titled, "How to get thing done", and it is collected in The Benchley Roundup, and Chips off the old Benchley. It proves that cat-vacuuming is not a new phenomena, just a new terminology.

It is available to read online at:
http://www.hackvan.com/pub/stig/etext/how-to-get-things-done-despite-procrastination.txt