I think that many active developers of FOSS projects are writing blogs about the development.
Often, these blogs give some insight on how things are evolving in the project, contain example code or discuss design decisions. Thus, I think these are interesting resources that could be added as links to an ohloh project description.
However, there is no such category available when adding links and I don't think that manual, tutorial or forum applies.
Therefore, I would suggest to add "Blog" as category for links.
Regards, Dieter