cweath,
What kind of 3D animation would you want to do? If you just want to do 3D text or extrude a logo then the easiest and best looking route would be Zaxwerks 3D invigorator for After Effects. If you wnat to do character animation or complex objects, Cinema 4D or Maya or many others.
If you have FCP, there are a ton of cool 3rd party plugins the help you animate in the NLE, from Boris, Eureka!, etc. and Kevin Monihan’s book Motion Graphics and Effects in FCP is a great way to get started.