Running some WPMU sites with multiple blogs and many varied topics. They each have plenty of content and gather more each day. I get some traffic, but want more. I'm already doing the twitter/facebook pages deal and have some traffic from there as well. I just need to come up with more organic search results. Since I can't just target a few keywords, as there are hundreds of blogs with different keywords, anyone have any thoughts/suggestions on how to go about gather more traffic for a blog farm type setup?