You need to offer something of value. Ask your self what can I offer that the other site's don't have..

Also try to build incoming traffic. You can have the best site in the world, but if you dont have a traffic and marketing plan, you will sit their and waiting for traffic..

Setup a blog and submit blog directories, the same for articles and submit to article blog directories. Their are many other ways to get traffic, do a search on this forum ..

Like cscgal has said, their are many forums online with your topic, I thinkg what you should do is sub niche niches topics..

But I would advise build traffic first..