I've been trying to decide the best format to write my tutorials in lately. The Wiki site at http://community.crystalspace3d.org is nice now that I have editing rights - people can offer feedback and the HTML/CSS layout seems fairly sane. I was also looking at Texinfo, which is what the Crystal Space documentation is written in.
I've authored pretty much everything in OpenOffice, which I've been very happy with. Recently I've just been doing straight HTML exports (which are freakin' HUGE) and PDF exports which I post to my old IU Computer Science account. I don't want to leave them with that burden permanently, tho.