Having large groups of content that all revolve around the same topic will build more relevance around keywords that you're trying to rank for within these topics, and it makes it much easier for Google to associate your content with specific topics. Not only that, but it makes it much easier to interlink between your content, pushing more internal links through your website.
Monster-Traffic is another traffic exchange, though it’s initially a little off-putting due to the 1995-style website. It’s a free for all styled advertising list, where anyone signing up becomes part of the audience and an advertiser at the same time. You sign up and you can enter a link into their system, and that link is added to a roster that is send out to every member of the group. Additionally, registration allows a free solo ad; an ad that isn’t drowned out by other advertisers in that mailer.