For the eZ components we are currently writing introductionary tutorials for each component. These tutorials should be a first start in understanding the abilities of each specific component without having to go through the full API documentation.
As good programmers we hate to document and thus the easier we can make the process the better documentation we will get. For our internal documents we use plain text files in SVN, describing guidelines and conventions. Those text files are formatted using reStructuredText , a format used by the Python community. It is a very easy to remember syntax, wiki-like, and it is easy to convert to HTML. We also decided to used the same format for our tutorials because it is such an easy format. With a specific PHP script we generate HTML from the tutorials, and add links to the other documentation that is generated by phpDocumentor from our inline API documentation.