Help / user documentation software

[JerryMungo]

I am looking for software to assist with creating help / user manuals. I'd like something that allows us to create offline and web based pages without having to maintain separate docs. I also need something that will allow us to create one master doc with a show/hide depending on the 'flavour' the user wants - we have multiple versions of our software interface for different countries.
Anyone had to do something similar? What have you used?

This is also posted in the development thread in case someone who doesn't read either thread has some input. Thanks!