Look at some of the huge website networks: About.com, Suite101.com, AllInfoAbout.com, BellaOnline.com, etc. Take a look at their general categories: Music, Movies, Business, Technology, Education, Science, Travel, Sports, Food, Health, Jobs ... I think you get the idea. They're all general purpose sites, but they do well because they segment the site to reach different groups. Of course you could try to do that with a forum. You would just need to separate it into different sections. You could promote the site as a whole, and you can do separate promotion (slightly adjusted banners and such or linking on niche sites to specific forum areas) for each topic in the forum. The good thing about a forum like that would be that readers could "cross over" to talk about their other interests. Personally, I'd love to see a forum where I could talk about everything from freelance writing to business to languages to music. It would be great to see it all in one place, almost like building a little online town with lots of small shops, rather than just a small niche community focused on one topic. It would be different, and I think you've got a good idea if you handle it properly. And w/ a good idea, why not make money? It's great that you want to do this as a hobby, but bringing in some ad revenue wouldn't hurt, and it could cover the hosting fees and such, especially as your audience would grow.