I have built a fairly successful forum before and sold it so I sorta know how to market but I would like to have less competition in my next niche. Hear are my new ideas for a forum. "Above top secret" style forum but more about things on earth a pet forum a movie forum a forum about blogging a forum for teens- I like this one What has the least amount of competition? I will be able to market as I know how to do that I just don't want the competition so I have less of a fight getting to where I want to be.
I highly find pet forums boring. There are tons of movie forums and general forums have a movie section. Bloggers tend to read blogs about blogging and not necessarily join forums. If you look in directories, there is a section for teens lol.
Pet Forums: http://www.theforumfinder.org/recreation/pets/ Movie Forums: http://www.theforumfinder.org/arts/movies-television/ Blogging Forums: http://www.theforumfinder.org/computers/internet/blogging/ Teens Forums: http://www.theforumfinder.org/society/teen-support/ ie lots of competition. You have to offer something that the other do not.