1-347-514-7296 is a phone number that automates this. Add it to a conference call, and frustrate the caller with no additional work. http://Reddit.com/r/itslenny is the closest thing it has to an official site.
You do have to get whitelisted though, last I checked. I was able to use it one time and now if I call it I get a message about whitelisting. Same for JollyRoger.
Yes, it burns their time. I just put them on speaker phone and continue working as usual on my computer, occasionally uttering a "yes" or "what's that?" when they tell me for the hundredth time to go to some phishing site. It's astonishing how long it takes for them to give up.
When working from home this is one of the few joys/social interactions if the day :D
Keep them on line by being a very dumb customer until they start cursing and hang up on me. : - )