One of the interesting aspects of using Apple’s Final Cut Pro editing application and the associated Final Cut Studio is the community of users and developers that has grown up around it. FCP primarily uses two plug-in architectures – FxScript and FxPlug – that permit easy third party development. The original FxScript is simple enough that many users can create new or modify existing effects with little or no programming expertise. In fact, Apple even offers documentation for creating new custom effects. Since FxScript doesn’t offer any copy protection hooks for developers, many of these plug-ins are offered free or at very low cost by their developers. Like Adobe After Effects or Digidesign Pro Tools, the power and potential of your Final Cut editing station can be greatly enhanced through the addition of a few choice plug-in packages.
You can search out the web and find many sources for these. Here’s a short list in no particular order of some of these resources for plug-ins and other extras. Enjoy!
EDIT: Please go to the top page “The Final Cut Ecosystem” for a more current compilation.