How Can You Find Relevant Catagories for a Niche?

My 2 core money sites are sort of not too common type niches. I have Wicked Article Creator that finds Categories depending on a drop down list but still non are very relevant. Does anyone know a good way to define good categories for a project?

Understand your relevant content better, have some experience with manually link building will help. I can't figure out something else

maybe visit some of the bigger article- and web-directories (goarticles, dmoz, ...) by hand and take notes which categories suit your niches best.