[Cialug] Open Source Documentation

[Nathan C. Smith]

What is the best system to use to create end-user documentation for an
open-source project?  

Is there something that can be used to assemble pieces in a book and then
produce them as text, html or PDF?

Nice to haves would include something that allows for collaborative
authoring, even merges and versions and web-based entry or editing.

Is Doc Book more of a spec than a project or product?

thanks.

-Nate