O'Reillys, Nat Torkington transcribed some of the Long Tail Panel at Supernova 2005. The thoughts were interesting (a rock radio station dies everyday), but it tweaked one of my not quite pet peeves.
Long tail disciples almost uniformly refer to the need for tools to "filter" extraordinary amounts of niche content. A better analogy is probably "navigation", avoiding the term search as search is highly conflated with information retrieval techniques. My guess is that if you look at how people deal actually deal with long tail ecologies (e.g. electronica DJs, comic book collectors, etc.) they navigate social networks surrounding and embedding the niche media.
If you look at Amazon, I would bet that the "People who bought...", Listmania, and review features work a lot better than the recommendation engine in terms of encouraging sales. These could only loosely be construed as filtering.
Instead of filtering tools, how about "expansion" tools? Tools that work from a kernel of known preferential content, and expand the horizon outward. You don't need to sell folks on the entirety of the long tail at once.