Some useful links:

Hauptwerk.cz: a page dedicated to Hauptwerk projects (organ sampling) in the Czech republic.

Haupwerk project Web site: a perfect software for virtual organ emulation.

How to build a MIDI console at home - an itinerary of the work

Virtually Baroque: James Pressler, the page of the Phantom organist

OrgelBits: Web pages of Dieter Thomsen dedicated to the promotion and reviews of Hauptwerk virtual organ consoles. Predominantly made for German speaking people. You may find my virtual organs reviewed there.

MyOrgan: software sampler for emulation of a pipe organ. The advantage of it is that it is free, but it has numerous disadvantages. It loads only Hauptwerk 1 style of sample sets, it does not allow for sophisticated features (no possibility to change tuning, voicing, lack of high quality tremulant and enclosure models, no possibility to load samples above 16 bit quality and 44.1kHz and numerous others)