Frontline-pcb
Frontline Genesis 2000 & GenFlex, This is one of the most popular of the big boy CAM systems. It has integrated design analysis with automatic data optimization. The basic modules include auto input the main graphic editor design analyzers and output. There are also many advanced modules available. GenFlex is designed with extra features which are designed for the Flex manufacturers. 

Pentalogix
Cam Master, is their top of the line Gerber editor it has may powerful features like; DRC, Netlist Extraction, Netlist Compare, Filleting (Teardrop or Snowman), Venting, these are the main options. Input formats are Gerber rs274-D, Gerber rs274-X (extended), HPGL, Excellon, Wessel, Sieb+Meyer, DPF, ODB++, Netlist (IPC-356), and Bitmap (.bmp). For more information as well as a Free Version of ViewMate check out their website.

Router Solutions
CAM-CAD Graphics B, This editor has the option of reading in may different formats including, Gerber, Autocad ADI & DXF, Barco DPF, Cadence Allergro (IPF), Case Plot, DMIS V3, Excellon, HP EGS Archive, HPGL, HPGL2, IGES, and IPC 350 -356- 356A

DownStream Technologies
CAM350 delivers unprecedented usability and performance. It eases the inspection, preparation, and manufacturing of PCB designs, increases speed and accuracy of all processes, and ensures optimal fabrication. Input formats are Gerber rs274-D, Gerber rs274-X (extended), HPGL, HPGL2, Excellon, Sieb+Meyer 1000 & 3000, DXF, ODB++, Netlist (IPC-356-A & IPC-356 & IPC-350), ECAM, and the following design file formats:(Mentor, GenCAD, Pads, PowerPCB, Zuken-Redac, Tango PRO, Accel EDA, PCAD 2001). Export Formats include Gerber, Excellon, DXF, ODB++, IPC-350 netlists. For more information as well as a Shareware limited version check out their website.