Ghostview for PostScript
Check out http://netlib.bell-labs.com/who/wim/ghost/index.html for a PostScript viewer for Windows.

Editors
<incomplete! for now try www.shareware.com>

Operating Systems
Though we don't officially support Unix, you might want to check out Linux, which you may obtain for free. Most of the software used in this course has versions that run under Linux. See David Schwartz's Unix page, also.