SUZANNE HICKEY  This was an invaluable tool for me to find a hidden volume of old video crap (75 gigs!) and delete it. Thanks for freeing up my hard drive to process everything!  
(Version 1.0)

FREDDUCKER  For anyone who comes from OS 9 and has used disk surveyor in the past, this app is a bit confusing graphically (only files are displayed graphically, and not folders sadly). I have also used an app called Disk Sweeper which I thought was more intuitive, and Grand Perspective which I thought was faster to load and used less CPU.  
(Version 1.0)

DIEM  doesn't get much easier than this...seriously. I used it, and 20 minutes later have cleared 20GB away of *stuff*.   
(Version 1.0)

KZX72  excellent little app...though it needs a cooler looking icon :)  
(Version 1.0)

ALJUK  This app is superb! It's amazing how something so simple can be so jaw-droppingly useful... I freed up 6GB on my 40GB iBook the first time I ran it, on superfluous spuff that I didn't have any idea was eating up that much room.

This app is a "must have".  
(Version 1.0)

BOB_TM  Ever felt the need to know where your disk space is going? Having been a faithful user of SpaceMonger for Windows, I've been on a lookout for similar tools on other platforms and this is a stiled-up version for OSX: It lets you uncover how iLife and GarageBand is filling up your hard drive and how old iPhoto-catalogs are claiming gigabytes.

I can but recommend this program. If you make it a part of your Mac life, consider donating.  
(Version 1.0)

THAT KID FROM OMAHA  Universal Intel version available as beta at: "http://www.derlien.com/dixforum/viewtopic.php?t=62"  
(Version 1.0)

JJH  This program is a GODSEND! I can't believe it is free. And it is GORGEOUS! Seriously, this program is the absolute best way to see what is taking up space on your HD. It works wonderfully/amazingly/beautifully. I am happy to have it. It is my friend. Thank you.

OH, and the plugin idea works perfectly (gives you right click support to see the graphical contents of a folder). In the prefences menu, there is a button to install the plugin if you want it, and a button if you want to uninstall the plugin. Right-click saves me that much more time. I love it.  
(Version 1.0)

ANONYMOUS  Author is distributing software with embedded debugging symbols - you download a folder containing over 5 MB uncompressed. The executable bundle built for deployment is about 300kB. Use the source code, Luke.  
(Version 1.0b)

ANONYMOUS  Just another cool visualization link: www.cs.umd.edu/hcil/millionvis/ (an open source C++ library for Interactive Information Visualization).   
(Version 1.0b)

ANONYMOUS  sounds great, really want to get my hands on it, so why can't I download it?

I've searched all over the web and every link takes me to a web page filled with jargony symbols! What's going on? Anyone else having these problems?  
(Version 1.0b)

ANONYMOUS  it's really k3w1 and all, but I find OmniDiskSweeper more useful  
(Version 1.0b)

RICH  This is really useful! Thanks! I'm running it on 10.3.6.  
(Version 1.0b)

ANONYMOUS  From the readme (for 0.8):

System Requirements

Disk Inventory X should run on any computer running Mac OS X 10.2 (or newer). I recommend at least 10.2.4.

So far so good on 10.2.8 for version 1.0b...

Excellent gaphical view of disk contents...  
(Version 1.0b)

SIMON WOLF  Disk Inventory X allowed me to track down a rogue file that had just filled around 25GB of hard disk space in a few minutes rather than relying on a lot of manual searching.

The tree view of a disk's directories along with their sizes is very useful and intuitive and I will now use this application to help me do some tidying up.  
(Version 0.8)