Important Automator/Action Development and Tutorial Links

Automator AppleScript Actions Tutorial
The Automator AppleScript Actions Tutorial shows you how to create an action for the Automator application using AppleScript as the implementation language. The tutorial assumes that you are familiar with AppleScript, but otherwise has no other prerequisites. It is helpful, however, if you have some experience with AppleScript Studio. [pdf]

Release Notes: Automator 1.0.1
These release notes provide the latest information about important issues for developers and scripters creating Automator Actions. The AppleScript debugger will now display variables, step, and stop at breakpoints correctly in action scripts. You can also use log statements inside scripts to log information to Xcode’s Run Log, but there is one caveat. A simple log “inside foo” will work at the top level of a script, but within a tell block, you must use tell me to log “inside foo”, as noted in the description for the log command in the AppleScript Studio Terminology Reference.

Automator Objective-C Reference (Objective-C)
The Automator framework supports the development of actions for the Automator application. An action is a bundle loaded by the Automator application that performs a specific task, such as copying a file or cropping an image. Using the application users can construct and execute workflows consisting of a sequence of actions. As a workflow executes, Automator passes the output of an action to the next action in the workflow. Automator loads action bundles from standard locations in the file system: /System/Library/Automator, /Library/Automator, and ~/Library/Automator. [pdf]

Automator Programming Guide
Apple as updated its Introduction to Automator Programming Guide. There appears to be some significant changes. [pdf]