This is something that I've been learning more about lately, so I thought I'd pass it along.

For those who want to apply your 3D animation skills and talent to the special effects field, you should at least learn a little about compositing. Here's an excerpt from Wikipedia:

In visual effects post-production, compositing refers to creating complex images or moving images by combining images from different sources – such as real-world digital video, digitized film, synthetic 3-D imagery, 2-D animations, painted backdrops, digital still photographs, and text.

Compositing includes everything from what your probably normally think of as special effects, where things explode, evaporate, morph, etc. It also includes stage extensions (making the scene stage larger digitally in post production), to environment creation (anything from buildings to complete worlds), to blue/green screen replacement (shooting in-front of a blue or green screen and then replacing the background with digitally created footage or footage shot elsewhere). Basically, the art of taking live footage and blending it with computer generated footage would be considered compositing.

Software

A few of the big compositing applications out there are Adobe After Effects ($999), Autodesk Combustion ($995), and Apple's Shake (recently slashed to $499). There is also a free open source compositing program called Jashaka (FREE). With the exception of Shake (Mac only), all of these apps are available for both Mac OS X and Windows.

Learning Resources

A couple of great resources I found are a podcast and a book. The podcast is called "The VFX Show" and the book to check out is "Digital Compositing for Film and Video" by Steve Wright. You may also want to check out VFXTalk for news and forums.

Hopefully this information will help you find out if compositing and VFX is something you would like to dive deeper into. It's an interesting field to use your animation skills in.