SCPOP is another interesting software I have played with. SCPOP gives to the owners of the Roland Sound Canvas midi modules the possibility to recreate the true sounds and the playing style of a real pipe organ by use of their midi synth.

The site of Raffaele Diodati & Filippo Tigli, authors of SCPOP- lots of resources...  http://www.scpop.de/

The SCPOP Box- run SCPOP without a PC... http://c.business.t-online.de/works/box.htm

Paul's SCPOP Organ project... http://www.angelfire.com/mn/organlcms/organpro.html

Lynn Walls SCPOP Organ project... http://cwalls.no-ip.com/home/midi.html