'Little-known Fact #6875:
There has never been a comic called "The Parking Lot Is Full".'
As of May 5, 2002, PLIF is done. Jack and Pat have a letter up on the site underneath the last comic, which explains their decision, saying, in part, that "the two of us have basically outgrown both the form and the content of the comic." The end comes as no surprise to some regular readers of the comic, who correctly guessed that it would be done when the Rocko & Socko storyline (the only continuous storyline in the comic's history) came to a close.
I must say, it's provided me with a lot of laughs over the years, and I'll miss the twisted humor. However, Jack and Pat state that they intend to leave the site intact, so we should be able to enjoy the many, many comics in the archive for years to come.
If they do leave the site exactly as it is, you should be able to find the last comic and accompanying letter at: http://www.plif.com/thisweek/thisweek.htm