for CAD/CAM, Rendering, fluid dynamics, vector graphics, and
One great place to look for graphics apps (at least half of your list) is at SAL-Scientific Applications for Linux. http://sal.kachinatech.com/sal1.shtml
scanner software:gimp-sane, kooka, many more
CD burning sofware:
try xcdroast, kreatecd, gtoaster(or is it gnometoaster), and k3b (off of the top of my head).
for winrar replacement: do you just want a utility to un-rar rar's, or do you want a do-it-all suite?
for the former, I don't know of any open source programs that can extract rar archives, but you can use unrar http://www.linux.org/apps/AppId_488.html