I'm looking to build a new system for my sister, and she runs a lot of AutoCAD. Are there any specific video cards I should be looking to get her or will a regular video card do?
Any regular video card will do for moderate AutoCAD work. It's when you get into hardcore 3d modeling that a professional graphics card becomes worth the huge price tag.
I run AutoCAD on an AMD 2400+ n/m and an Nvidia Gforce 440mx and it runs fine. Even in 3D, however if you get some really big files I'm sure it would slow it down.
I use AutoCAD 8+ hours a day, 5 days a week on a GF2 GTS. AutoCAD is simply not a demanding graphics program. If you want really good 2D look at Matrox. Else any low end ATI or NVIDIA card should suit you fine. A 3D modeling app like SolidWorks, Maya, etc would be more suitable for a profession video card (Quadro, FireGL, etc).
My teacher in drafting right now uses integrated graphics on a Pentium 3 machine. Not only is AutoCAD (2D and some moderate 3D) good with these graphics, but so is SolidWorks (the best 3D Sketching tool ever )
So yeah, a good old $50-$75 card will be more than sufficient.