Adobe Illustrator
Vector image creation/manipulation.

Macromedia Freehand
Vector image creation/manipulation.

Equilibrium DeBabelizer
Raster image manipulation.

Flash
Flash animations, vector graphics.

Adobe ScreenReady
Batch image rasterization.

Fractal Design Painter
Vector image creation/manipulation.
 
Photoshop Plug-Ins
Photoshop GIF89a Plug In
Grab this plug-in filter to create transparent GIFs.

BoxTop Photogif
GIF export plug-in for Photoshop.

BoxTop ProJPEG
JPEG export plug-in for Photoshop.

HVS JPEG
JPEG export plug-in for Photoshop.

HVS Color GIF
GIF export plug-in for Photoshop.
 
Gif Animation
GIFBuilder
(version 0.5 is buggy) Simple to use, animated-GIF-assembly tool.
 
Image Viewers/Converters
GIFConverter
Shareware utility for viewing images and converting between file formats.
 
HTML Editors
BBEdit (MacOS)
HTML creation, editing, scripting, heavy text work.

Dreamweaver
Visual webpage creation with direct access to HTML coding if desired.
 
File Transfer/Preferences
Fetch
Drag-and-drop file transfers to and from any machine with an FTP server, over a TCP/IP network.

NCSA Telnet
Allows simultaneous connections to numerous computers across the network plus a standard file transfer server (FTP).

Internet Config 1.3
Global Internet preferences setting.
 
Layout/Typography
PageMaker
Layout.

Quark XPress
Layout, typography.

Adobe Acrobat
Formatted document portability.

Adobe Type Manager Deluxe
Font management and enhancement.

Adobe Type Reunion Deluxe
Font management and enhancement.
 

Miscellaneous
DitherBox
Dither-pattern generator.

ImageMapper
Image map creation.

Small Screen
Different screen/monitor checking.

ScreenRuler
Screen measuring.

Flash-It
Screen capture utility.

Gamma
Comes packaged with Photoshop; monitor calibration utility.

WebMap
WebMap reads GIF and PICT files, and allows you to draw out the various graphic primitives (rectangle, circle, and polygon) that represent the hot areas on an html image map.

RGB/Hex Converter
This site has a script running that will convert RGB values to hexidecimal and vice versa.

 
 
Windows
 
Image Creation Software:
Adobe Photoshop
The most powerful graphics software available.

Adobe Illustrator
The finest illustration tools and typographic control at your fingertips.

Corel Draw/Photopaint
Although not as powerful as Photoshop, the Corel family of graphics software is a good choice for creating graphics on the Web.

Fractal Design Painter
Innovative features make Fractal Design Painter a good choice for creating graphics.

Gif Animation
GIF Construction Set
Powerful tools allow you to create animated GIFs.
 
Image Viewers/Converters
Lview Pro
Shareware utility that for viewing and converting between file formats, as well as making transparent GIFs.

HTML Editors
Homesite (Windows)
HTML creation, editing, scripting, heavy text work.

Dreamweaver
Visual webpage creation with direct access to HTML coding if desired.

 
File Transfer Protocol
Cute FTP
Shareware FTP program with an excellent user-interface.

Telnet
CRT
Easy to use telnet application with lots of configurable features.

Miscellaneous

Map Edit
A graphical editor for World Wide Web image maps. Very simple to use.

Color Manipulation Device
Useful utility that allows you to specify hexidecimal values in your HTML documents.

RGB/Hex Converter
This site has a script running that will convert RGB values to hexidecimal and vice versa.
 
Single Pixel GIFs
Here's info how to make your own single-pixel gifs!