[]IMO if you have a niche you can contact companies in the space and have them advertise their products.[/]
That really depends on the niche, if it's in a "Hot" market niche then yes, if not maybe no really depends on the market.
[]I have seen some of your other sites, mostly to get an idea of how much traffic you have, and I'm sure we are in the top 3 from a revenue standpoint. [/]
Who's the number 3 guy?

[]I don't like the idea of charging members because that can create resistance for folks to join. In our auto niche, all the sites are free to users so we can't charge anything to folks.
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Yes, in your niche I agree, there are way to many free performance car sites out there, I don't think you could get away with it.
It just boils down to "Your" nich and knowing your viewers and potential advertisers, what works great for one site may not work at all for another.
For "Me" I found the best to be a hybrid approach, sell advertising viewable by non-members with limited access but access to the most popular parts of the site, and offer full access and more benefits with an "ad free" experience to supporting Members.
By doing this I can gain revenue from non-members, members and advertisers

the benefits to the viewer are the site stays free to them but they also have the option of not having to view tons of advertisments, so I think everyone wins.

But the important thing if you want to make money with a website is offer a great source of info your readers need/want, content is king, and know your viewers. No two sites are the same even in the same niche so webmasters have to do a lot of market research.