Right, for those of you starting with 3D or like to learn a bit more about it, here's a short list of info to get you started.
Unlike the (static) 2D scene, the 3D scene has no clearcut 'standard app' that reigns supreme over it's competition. The world of 3D knows many many many apps that all are useful in their own little way. However, there are 4 prominent marketleaders, these are:
3DStudio Max (
http://www.discreet.com/products/3dsmax/), made by Discreet (
http://www.discreet.com). This is a jack-of-all-trades, used predominantly in the games industry, but a fair amount of use in just about any industry.
It's plus points are it's versitality, it's relatively easy interface (remember folks, 3D isn't as easy as photoshop) and the utterly massive amounts of plug-ins available, meaning you can extend max to do just about anything you need it to do. Also of interest is it integrates heavily with Discreet's video compositing app Combustion, and has tons and tons of educational material out there as well as a huge userbase (i.e. help community).
Downsides is the price (where other 3D apps have plummeted their prices to an all-time low, Max has stood it's ground), the fact it's not the most stable piece of software around and it's restricted to the Windows platform only.
Noteworthy info: Max doesn't have a free learning version available, but Discreet do have the free Gmax (
http://www.discreet.com/products/gmax) they give away, a prog aimed at game mod makers. Also, for those with limited 3D needs, they've created Plasma (
http://www.discreet.com/products/plasma/), a cut down version of Max with a more photoshop-esque interface, aimed solely at web3D (shockwave & Flash). Check 'em out.
Maya (
http://www.aliaswavefront.com/en/pro...ya/index.shtml), made by Alias|Wavefront (
http://www.aliaswavefront.com/en/news/home.shtml). This one just won an oscar, and is the premiere app used in Hollywood. The focus of Maya is character animation, and that's it's big strength. It's also used in the video & games industry (thanks to it's recent massive pricecut).
It's plus points are the 'node-based' way of working (everything is a node that you connect to other nodes making your project very flexible and easy to manage), it's open architecture (meaning you can code extension to it to make it do whatever you want) and it's robustness. Also Maya is available on Irix, Linux, Windows and Mac, making it truly cross platform.
Downsides are the steep learning curve, the not-to-great renderer (hollywood all use renderman anyway, so they don't care about the native renderer) although recently A|W are giving away Mental Ray (a great renderer) for free with Maya. Ultimately this is a big app that'll take a fair bit of time to get to know.
Noteworthy info: A free learning version (
http://www.aliaswavefront.com/en/pro...le/index.shtml) is available. It uses a custom fileformat, restricts renders to a certain size and puts watermarks on the renders and viewports. But hey, it's free and it comes with a buncha tutorials.
Lightwave (
http://www.newtek.com/products/light...uct/index.html), made by Newtek (
http://www.newtek.com). The quirky one of the bunch. Modelling and animating/rendering are split into two apps (great according to some, stupid to others) and the interface is straight from the Amiga days. Lightwave is known for it's excellent modelling and rendering though, so if you like quirky things, check it out. Ligtwave is mainly used for TV and video productions, with a small presence in the games and movie industry.
It's plus points are it's relatively cheap price (cheapest of the bucnh) it's great modelling tools and good renderer. The user community can be called dedicated (to the average lightwave user lightwave is the best thing *ever*) or fundamentalist even

. It's available on both Windows and Mac, as well as having a linux renderer (for you renderfarm owners ;P ).
Downsides are the quirky interface, the splitting of modelling and animating/rendering (depending how you look at it) and the lack of a lot of 3rd party documentation.
Noteworthy info: There's a free learning version (
http://www.newtek.com/discovery.html) available.
XSI (
http://www.softimage.com/Products/Xsi/v3/), made by Softimage(url=http://www.softimage.com). Together with Maya this is the other mainstream high-end 3D app. XSI is the follow-up to Softimage 3D, which was the main app hollywood used before Maya came along. Now they're growing back fast and giving Maya a run for it's money. XSI is used for movie and video productions, with a small usage for games.
It's plus points are it's friendly (tho some say cluttered) interface, it's great subdiv tools, non linear animation, built-in compositing engine and excellent renderer (mental ray). Again this is a big deep app that'll take quite some time to get to know. XSI is available on both Windows, Linux and Irix.
Downsides are the steep learning curve, price and some features (like NURBS modelling) are incomplete.
Noteworthy: XSI also has a free learning version (
http://www.softimage.com/products/exp/v3/), which is pretty non-instrusive (small watermark on the render).
Ofcourse there are tons of other 3D apps, with each a respectable userbase, but these are the 4 biggies.
Ok, so. You're new to 3D and want to start. You could download some of the free learning versions mentioned above and toy with those. Most likely tho you'll be kind of overwhelmed with all the concepts of 3D (polygons, nurbs, subdivision surfaces, xyz axes, uv mapping, isoparms, need I go on ;P ) and the often confusing interfaces. You can do the supplied tuts, but if you're like me you just want to dive in without reading 400 page manuals first.
So head on over to
www.wings3d.com (
http://www.wings3d.com) and grab Wings3D. It's a free opensource polygon modelling program, that has attracted quite some attention from 3D pros for it's super simple but very powerful modelling method. The interface'll take you 10 minutes to learn. After that it's modelling goodness.
Once you feel you're kicking ass modelling wise, then grab a learning version of whatever 3D app that appeals to you most. Do the tuts, or head over to
http://www.3dbuzz.com and download some training vids for Max, XSI or Maya totally free. Then start to learn about animation, lighting, mapping, rendering, etc, etc.
Edit: I cleaned up the URLs, with the conversion to the new system they got messed up.