I spent most of the day yesterday banging my head against the learning curve for producing .Net api documentation.  In the past, when working for an employer who was willing to pay for it, I produced documentation using a commercial product.  That product was more or less an interface that interacted with my classes within visual studio and, when I was producing additional content, hid the markup from me, so that I was looking at a a WYSIWYG interface.  Behind the scenes, the compilation of the .chm file was still done by MS Help Workshop--a product that hasn't been upgraded in ages.

More than once, I've thought that there ought to be an open source way to produce documentation for an opensource project.  The tool for this task in the past has been NDoc, but more recently it seems to have been supplanted by Sandcastle, a set of command line programs developed within MS and distributed through Codeplex.