The New York Times has an article profiling Next New Networks, an online television startup backed by former executives of MTV and Nickelodeon. They've launched with 6 "channel" sites, taking advantage of the "long tail" by focusing on niche topics such as fashion, automotive and comics. You can view a complete list of all 6 sites here. This model of building a network based on niche content is certainly something that's proved itself online. It's the same model that blog networks such as Gawker and Weblogs, Inc. have built themselves on.
Keep an eye on these guys. Link via AdPulp.