Amateur Telescope Maker Optical Software
ATMOS is an optical design and analysis software program for designing and analyzing telescope configurations. [Freeware Download]
http://web.tiscali.it/ATMOS/

Cell
A floatation mirror cell design software program for reflecting telescopes. [Freeware - DOS]
http://www.davidchandler.com/cell.htm

Aberrator
Generates star-testing images to show all the common telescope defects: astigmatism, coma, pinch, tube-currents. One can specify the charateristics of the scope as far as diameter, obstruction, spider. [Windows Freeware]
http://aberrator.astronomy.net/

Java Script
Provides several JAVA applets designed to assist amateur astronomers and telescope constructers.
http://members.kabsi.at/i.krastev/java/atmjava.html