Catching up on "long tail" startups I know of :) Feedmil is a startup out of Seoul National University in Korea led by Prof. John Park. More from their site:
"Feedmil is a feed search engine featuring a spam-free, topic-focused search for a variety of feed types including blogs, microblogs, public and social media feeds as well as podcasts. Feedmil’s goal is to help people search feeds of interest in the most efficient and easiest possible way through the use of innovative technologies and user interfaces.
Feedmil improves the entire feed search process. In the search interface, feedmil allows users to specify not only the query but also the popularity range of feeds, enabling them to quickly discover high quality but less popular feeds located in the long tail of millions of feeds. On the search result page, feedmil gives a new feed search experience that is focused on quality and topic relevance beyond just popularity. With powerful slider controls for adjusting topic significance, users will be able to get more accurate results and at the same time explore the feeds they like serendipitously."