In the spirit of this question on stackoverflow.com I would like to compile a list of open source/creative commons/public domain technical guides. My original thought was to list books only for operating systems but we might as well open it up to other technical guides that people may find useful not to include programming languages, as that as already been done on stackoverflow.com, as referenced earlier. I think we might want to skip anything too esoteric however... My preference would be books in PDF, or other printable formats, not so much web guides.
To start it off I will list two excellent FreeBSD books:
Of course the Magnum Opus FreeBSD Handbook
And another great book The Complete FreeBSD
I would provide links but alas as I am a new user I am not allowed to post more than one link. A quick Google search of the above titles will get you right to the the manuals though. Alright, lets see what else is out there...