When you go to a retail store like Best Buy or Circuit City they are mostly selling the Consumer models which usually have larger LCD screens and some extra features like firewire that some business notebooks don't have.
But the case construction is a step down on most although some consumer models are still made better than others.
As Bob stated, IBM makes only business class notebooks and the hard drives also are designed to withstand more shocks and even minor drops. They have excellent keyboards. They don't make much larger than a 14.1" LCD but that is still ok for people who don't watch many DVD's or don't need the extra spreadsheet width you can get with a 15.4" widescreen. And they weigh 1 to 1.5 pounds less (if getting Pentium M Centrino model you should come in at 5.5 pounds or less.
The Toshiba Techra line is the business line and my wife had one for years with no problems with her Accounting firm. You can also access the Compaq and HP business notebook lines at hpshopping by selecting business when you access it.
Many students like the 15.4" (or home users who want an all around notebook) but I have seen several turn them in when leaving school for a 14.1" LCD business line notebook or smaller as that is definitely better for frequent traveling.
Also look at Fujitsu -- the toughbook is perhaps more than you need but worthwhile if you are really worried about damage (Panasonic makes a model like this too).
But the IBM or Toshiba Techra should give you a stronger chassis without going over $2,000 much.
Make sure you get a Pentium M Dothan CPU as that now has double the L2 system cache (2mb). The 715 1.5 Is a Dothan but the 705 1.5 is a Dothan so watch out for that. Anything 1.6 mhz or higher in a Pentium M new notebook (not a stale model) should be a Dothan and it should have a 7xx cpu number (1.6 is 725, 1.7 is 735, etc.)