To one of the other answerers: Maya, not 3DS Max was used in the production of Avatar.
I think you'll find that out in the world of CG, Maya is regarded as the leading industry standard for ANY 3D design (except architecture, which 3DS Max is there for - though virtually identical to Maya, just with features that make architectural design easier. Not knowing how to use Maya doesn't shut doors, but knowing how definitely opens them.
I've heard a lot of people who say that they used to work with Maya, and that they then discovered programs like Blender, Cinema 4D, and then this other one, and they've all said that they decided to move from Maya to these alternatives because they're easier to use and apparently offers as much control as Maya.
In my personal opinion, after having FIRST started working with Blender (an amazing free, open-source 3D modelling and animation program), then moving on to Maya, I've found that having some 3D knowledge with a simpler program, had helped me a great amount through the "steep learning curve" I've been hearing about from first time 3D artists using Maya.
I admit though, that because Blender and Maya are both very different in both UI, workflow, viewing & transform controls (both have quick keyboard shortcuts) there was an element of essentially relearning how to do things in Maya, but once you get past that, it proves to be far more powerful than ANY 3D modelling program I've used.
My advice is to get Maya, and also patiently work through the "Getting Started" pdf that Autodesk supplies on their website. Once you get past the learning, Maya will become an indispensable tool for anything 3D. (might I add, the "mental ray" renderer that is supplied for free along with Maya - though not considered right at the top of best renderers - still kicks *** and is easily better than the likes of those supplied by Blender and C4D.)
Oh - and in case you're interested, here's a list of all the software that was used in the production of Avatar:
Autodesk Maya
Pixar Renderman for Maya
Autodesk SoftImage XSI
Luxology Modo (model design, e.g. the Scorpion)
Lightwave (low-res realtime environments)
Houdini (unknown area)
ZBrush (creature design)
Auodesk 3ds max (space shots, control room screens and HUD renderings)
Autodesk MotionBuilder (for real-time 3d visualisations)
Eyeon Fusion (image compositing)
The Foundry Nuke Compositor (previz image compositing)
Autodesk Smoke (color correction)
Autodesk Combustion (compositing)
Massive (vegetation simulation)
Mudbox (floating mountains)
Avid(video editing)
Adobe After Effects (compositing, real-ime visualizations)
PF Track (motion tracking, background replacement)
Adobe Illustrator (HUD and screens layout)
Adobe Photoshop (concept art, textures)
Adobe Premiere (proofing, rough compositing with AE)
many tools developed in-house
countless plugins for each platform, some of them Ocula for Nuke, Ktakatoa for 3ds max, Sapphire for Combustion/AE.