In early versions of Mac OS X, you could get away with using cron to schedule tasks. Whether this was by accident or intentional, I don't know. When support for cron was removed, I wanted to seek out the Mac way of scheduling tasks.
In short, what I found were many cross references to iCal and Automator. It's all a blur to me right now and it was many months ago. If I recall correctly, the secret sauce in this bizarre new recipe is the special daemon process, launchd. The upshot is that my scheduled tasks no longer depend on my system running continuously. On systems like Linux, this problem could be solved by installing anacron.
This works well enough to fit my needs, but I miss the convenience of typing crontab in my shell and changing my scheduled tasks from the comfort of my favorite text editor. No fancy widgets, no fancy dropdown menus, just simple text manipulation.
Update: Just found out about launchd and LaunchAgents. Maybe I'll write a post on it someday.