z80 Documentation
Programming documentations and tutorials for the z80 CPU and the TI-83 calculator.
http://www.ticalc.org/pub/text/z80/

(Yet Another) IRC Information Website
Contains links, explanations, guides, and many good documentations.
http://users.tkk.fi/~jlohikos/IRC.html

Ccdoc
ccdoc for RISC OS: ccdoc is a tool that generates HTML documentations from C/C++ header files
http://www.arcsite.de/hp/ccdoc/

Purity Software, Inc.: WebSiphon
Web application server. Specifications, documentations, free trial version, tutorials.
http://www.purity.com/websiphon.ws

LAOLA
A collection of documentations and perl programs dealing with binary file formats of Windows program documents.
http://user.cs.tu-berlin.de/~schwartz/pmh/

FreeTechBooks
Free online computer science, engineering and programming books, ebooks, texts, textbooks, lecture notes, documentations and references.
http://www.freetechbooks.com/

PSTricks
Access PostScript capabilities inside (La)TeX, by Timothy van Zandt. Site contains documentations, bugs list, and examples of application.
http://tug.org/PSTricks/

SquareDesign
Graphic design studio located in Nijkerk, Netherlands. Packaging, corporate identity, documentations and Internet. In English and Dutch.
http://www.squaredesign.nl/

Commercial CP/M Software Archive
A collection of CP/M software, including source codes and documentations.
http://www.retroarchive.org/cpm/

Retrospective in Operating System Arts
Documentations on how to get various operating systems running inside Hercules.
http://open360.copyleft.de/