You have no doubt already heard of RaptureLetters.com. It's a "personal ministry" set up by Scott Butcher to help those left behind who may be struggling with trying to figure out "why millions of people have just disappeared."
It's simple. You enter a loved one's e-mail address into the database, and once that fateful day arrives a letter will be sent out (the process is described on the web site) explaining what has just happened and that there is still hope for salvation. You can read a sample letter here.
Unfortunately, there is no mention of the unspeakable and unparalleled period of tribulation the person is about to go through. (I guess he'll find out soon enough.) But the biggest problem I can think of is that the unsaved recipient of one of these rapture letters may have his spam filter turned on. What then?