FileZilla
Transfer files over the Internet.
OS: Windows 95/98/NT/2000/XP
Download here

Zip Central
Zip and unzip files.
OS: Windows 95/98/NT/2000/XP
Download here

Free Allegro Viewer
The Cadence Allegro viewer allows designers to view and plot any
Allegro PCB design.
OS: Windows 95/98/NT/2000/XP
Download here

Viewmate
Windows based Gerber viewer
OS: Windows 98/NT
Download here

VUV viewer
Gerber Viewer for Valor. Can also import ODB files.
OS: WindowsNT/2000, Unix
Download here