I got a Toshiba LapTop. 1.1gig Celery, 20gig hard drive, lan, modem, DVD, floppy, 14.1 screen, 256megs SDRAM, 16megs vidcard with monitor and TV out, ect... it is good comp. I have taken it all over the country and use it at work now and then being they are to cheap to buy AutoCad200X. It runs ACAD2000, SolidWorks2003, CorelDraw9, some older games, and DVDs smoothly. I paid $950 new for it 8 months ago. You should get a pretty good one for that now I would think.
Just make sure ytou actually going to use it on the road though. It is not worthy to replace a desktop. I did have at one time though it hooked up to a 17" monitor, regular keyboard, regular speakers (pluged into the earphone jack), and a USB mouse to replace my desktop while I modded it. Smallest, quietest, desktop I ever had.