One of the major benefits of Final Cut is a robust developer community, with lots of plugins. I started messing around with plugins about 3 years ago, starting with FXScript. FXScript is very simple, and allows you to write the plugins right in Final Cut. However, it’s not very powerful, and likely won’t be supported in FCP X.
The next step for plugin development is FXPlug, which has been around for awhile. By now, most major for-sale plugin developers are using FXPlug. FXPlug works in Motion and Final Cut, and supports both software and hardware rendering.
I’ve been working on learning FXPlug, and have found a lot less documentation than what was available with FXScript (which wasn’t much). FXPlug definitely has a much higher learning curve, which I think affects the type of community support.
I recently found this overview of FXPlug by Darrin Cardani, an Apple developer. It’s from 2007, and not great quality, but it is by far the best introduction and overview of the SDK that I have found. If you are familiar with Objective C, this quickly shows you the basics of FXPlug.
You can watch the video from Toolfarm.com here.