Debabelizer is an image import/export and manipulation application for Macs and PCs, developed by Equilibrium: http://www.equilibrium.com/.
When preparing graphics for the web you may use Photoshop, Paintshop Pro, Gimp, etc, etc. These all allow you to create and then save your beautiful graphics as gifs and jpegs, but battle hardened web designers use Debabelizer.
They don't use Debabelizer to edit their images, add text, or draw; they use it to convert the artwork that they've produced in one of the other programs into gifs and jpegs.
So why don't they just use save for web? To answer this question, and understand where Debabelizer fits into a web designer's toolset, it helps if we understand where Debabelizer came from.
De-Babel-izer was originally developed to enable designers and reprographics people to batch convert almost any graphics format, from almost any system, into any other graphics format. It could read image formats from SGI, UN*X, Atari ST, Amiga, and many others, in fact it was the only graphics converter that could read some of these files, apart from the original graphics package on the specific OS.
It included a simple way of recording actions on one image (such as cropping, resizing, recolouring) and then applying them to thousands of other images.
When the gif image format arrived in 1987, support for it was added. Equilibrium had already developed powerful algorithms for mapping true colour images onto a fixed size palette of colours that were considered amongst the best available. Because they were coming from a background of batch conversion, they also provided the ability to create an ideal palette (what they have called a super palette) for any number of images.
These technologies allowed web designers to produce better gif images, with smaller file sizes, just by pointing Debabeilizer at their web site. It also meant they could take a series of frames to an animation, find the ideal palette for all of the images, and convert them into the smallest animated gif possible, without any perceived loss in quality.
Debabelizer has lost much of its edge, both because file sizes are less important now internet connections are faster, and because the gif export capabilities of other graphics packages have improved. It still however, remains the package of choice for designers who need to fine tune their images for the best possible results.