I don't know if anybody on here does SEO for forums but I mainly run (try to run, can't seem to be successful with any of them) forums. I found a pretty good exchange site for forum posts. Some of the users make really good content. Some make generic shitty replies. But I figure it's worth sharing. It's called PostLoop.com and you can either make posts to receive some or you can buy them at 1,000 posts for less than $100. Oh yeah they comment on your blog too but idk why anyone would want to buy that.