Resources are currently divided into four parts:
[ Apple Computer | Links | Software |Mailing Lists ]

AppleScript GuideBooks (for OS 9 only)
Downloadable Scripts (mixture of OS 9 and OS X)
AppleScript for OS X - includes Toolbar scripts and Script Menu

Official Apple AppleScript Website
Mothership of AppleScript. Must go.

AppleScript Central
More downloadable scripts

MacScripter.net
Amazing collection of AppleScripts, 3rd party OSAX and home to Dialog Studio, a simple and cheap app to build more comprehensive user dialogs.

Virtual Training Company
A training company selling a very good CD of AppleScript tutorials.

TecSoft
A training company doing a lot of AppleScript work, and home to a good training CD too.

Smile - Script editor & integrated environment
Highly recommend for beginners because of the Balance feature and best of all, it is free!

Script Debugger - Advanced script editing application
Really cool app for non-beginners, who have working knowledge of how compilers work. Breakpoints and stuff like that.

Scripter - Professional AS authoring environment
I have not tried this personally, but it is a competitor of Script Debugger with more or less similar features.

FaceSpan - AppleScript Interface Builder
This application allows you to build the front-end to AppleScripts that behave more like a real application. Good for deployment work.

Apple's AppleScript-user List - AppleScript's the topic here.