If you are serious about CAD applications on your laptop you do not want a low end laptop like most of these suggestions. You have to make sure you have a dedicated GPU, a quad core i7 would be recommended and as much memory and disk you can afford. You also want to make sure it's set up to run as cool as possible and that it vents from the back or anyplace other than at your dominant hand (used for the mouse) and not from the bottom (it will burn your lap or not vent enough heat.). Here is a link to more detail
ClickyNot meant to put down other folks suggestions, but your day to day laptop will not run a decent 3D program and if it does run, it will take hours to render if you're able to render anything. Hope this helps!