Animation is a tougher program to buy for than many others.  First, you need to decide whether to go with an Apple Macintosh ® or Microsoft Windows ® based system.  I lean towards Windows for Animation students for several reasons.  First and foremost is that Autodesk 3ds Max ® (formerly Discreet 3ds Max, or 3d Studio Max) is a Windows-only product.  Specifically, Microsoft Windows XP ® (with service pack 1) or Microsoft Windows 2000 ® (with service pack 4).  This is a powerful animation product which is one of our primary learning platforms at our college.  Alias Maya ® is another piece of powerful animation software (it was used on Ice Age, The Lord of the Rings, The Perfect Storm, amongst others) that is primarily Windows based - it now works on Macintoshes as well, but for a while you could only get the Unlimited version on Windows. 

Dreamworks, for example, uses Hewlett Packard ® systems, as HP would be happy to tell you.  Though, I believe they use a proprietary Linux operating system and software for their animation.

Computer animation is one program where a laptop may not be your best bet.  Primarily, this is due to hardware limitation of laptops compared to desktops.  In general, you have more options for video cards in desktops than you do for laptops.

That being said, if you are going to look for a laptop, you really want to go all out and get one that is as powerful as possible.  Look for the most powerful video card you can (currently, spring of 2005, the NVidia 6800 Ultra offered exclusively on the Dell XPS2), the most memory, and the fastest processor you can afford.  If you are going the laptop route, you probably have enough money to get the absolute best, but I'd prioritize memory, then processor, then video card.  After that, look for a fast hard drive (something at least 7200 RPM, which can be tougher to find in a laptop).

As far as a desktop system goes, it's similar.  Obviously you need high-end systems, and when looking on the web sites of various companies, your best bet is to look in the "Workstation" category.  These will have systems and video cards that are engineered and tweaked for rendering, as opposed to gaming.  For instance, you will want to use an nVidia Quadro instead of the normal nVidia gaming video cards.  To find these, you may have to look in the small or medium business sections of a computer sellers web site. 

Again, lots of memory will be your best bet - you probably can't do too much.  Most of the high end animation programs can use most of the memory you'll be able to give them.  Minimum of 1 GB (Gigabyte).

A fast processor is the next thing you should focus on.  You might want to consider a 64-bit processor - while this is still more of a niche market, within a few years anything high end will start being written towards a 64-bit platform, as this should give us a great jump in speed.  Intel and AMD both have 64-bit processors now - look for the best price/performance.

Next, the video card, also known as graphics cards.  As stated before, you will be better off getting a workstation video card than one geared towards gaming.  These are engineered for OpenGL® graphics, which is what will normally be used for rendering your animations.  Look for items such as the nVidia Quadro ®, Ati FireGL ®, or 3dlabs Wildcat ® video cards.

Also, you'll want to look at hard drives.  Again, faster will be better with these, due to the amount of disk work involved in rendering your animations.  Probably your best bet as far as price vs. performance goes will be SATA hard drives in a RAID 0 configuration, with a minimum speed rating of 7200 RPM.  RAID 0 basically will split up the hard drive work between all of the drives, to help reduce the speed limitation of any one particular drive.  However, you should know that this does not give you any sort of disaster recovery, so if any one drive fails, you lose all of the data on all of the drives.  So, it's more important in a RAID 0 configuration than any other to make sure you are backing up your work!  You'll also want to get as large of hard drives as you can, since animation files are notorious for being large.

Last, DVD burner will be invaluable for a cheap method of backing up the large files your animations will produce.  Be sure to look for one that says it is a Dual Layer DVD burner, as these can store twice as much as standard DVD-R/RWs.