The following portals list works on Wikisource sorted by genre:
Portal:Christian fiction
Portal:Cowboys (covers Western fiction)
Portal:Horror
Portal:Cthulhu Mythos
Portal:Ghost stories
Portal:Gothic fiction
Portal:Humour
Portal:Adventure
Portal:Fantasy
Portal:Mystery (includes Crime & Detective fiction)
Portal:Romance
Portal:Science fiction
Portal:Thriller (includes Suspense fiction)