Back in 2003, I stumbled across a thread in the SomethingAwful forums. It was all about a college student whose mother's hoarding habits had more or less destroyed their house. The 5MB of photos this fellow posted left such a huge impression on me that I've never forgotten it; I use it in conversation sometimes, too, if my mother is troubled by the "horrible mess" in our living room etc. But until now, I hadn't been able to find those photos again to show her why a little bit of clutter here or there does not even come close to...whatever the hell this complete disaster is.
I uploaded the 50+ photos to my Flickr account, put them all in order, and added the commentary from the original thread (made by a user named "Knormal" - all credit for the pics and descriptions go to him). You can now go through them, shot by shot, and read the explanation behind the horrors of this you'll-believe-it-when-you-see-it state of affairs.
For the record, compulsive hoarding (or disposophobia - yes, that's a real term!) is, in fact, recognized as a legitimate psychiatric issue; it has not, however, been defined in the DSM-IV as anything more than an offshoot of Obsessive-Compulsive Disorder.
Without further ado, then, I shall direct you to START HERE, the very first photo, and wander through the house as though you were there yourself. Just be grateful that you're not.