A bulletin board is when lots of people make postings on different topics, and a discussion (thread) can follow. The bulletin board software makes it easy to see all the topics and see how many responses there were to each topic. Look at the blog for TIVO, the television video recorder: http://www.tivocommunity.com/tivo-vb/
In our current blog, if you want to find out what others are talking about you can either click on one of the pre-defined categories or just start at the top and scroll downward through all the postings. Some of the postings are quite long and have photos, etc, which makes it tedious to scroll through all of them.
Using bulletin board software all the topics would be listed as single lines. Scan the lines, click on a topic, then read all the responses. Users define the categories (topics).
I think what you are trying to do would work best as a bulletin board. Consider this software: http://www.vbulletin.com/
Hadley Callaway, MD