Here's one tip and probably the best tip you will ever get:
Create Reciprocal Templates With Links To Your Categories and Your Index!
I see many linklists do this and Im doing the same inside of my network and it WORKS! It's no rocket sience but it will give your niche pages deeplinks and your SE-rankings (NO PR) will benefit from doing that.
Good luck with your website, and also: FUCK PAGERANK, PR isnt gonna give you much more traffic
