TeX RESOURCES.
TeX is a powerful typesetting program that
has become the gold standard for producing written mathematics (and a
lot of other science as well). There are various enhancements and
flavors; many are free- or shareware. You are under absolutely no
obligation to use TeX, nor any other word processor or typesetting
program.
Some
basic
info
on
LaTeX
Some more
advanced info
American
Mathematical Society TeX resource page
TeXmacs.
Almost WYSIWYG, and it's freeware.
For Windows users, there is
an excellent editor, WinEdt
, and MiKTeX , a free TeX base.
If you want to use TeX for your homework, make sure and review the last few pages of the instructions for documenting your work. And check out this FAQ.
For dealing with PostScript, see e.g. Ghostscript, Ghostview and GSview.