Search Engine Forums, SEO Forum

That's a good list.

Those forums are the best to drive traffic.

Great list of Forums from which to drive traffic to your websites.

And you are right about the point that quality content is what will actually get your signature noticed by readers. Spamming will usually instantly get you banned and added to the blacklist.

I would say, social networking sites like Facebook has good number of audience and communities to get along with and get decent traffic.