Red Swoosh is making its peer-to-peer distribution channel available for free, supported by advertising shown to every fifth downloader. Their technology has interested me since I first heard about it on a Web 2.0 Show interview from BarCamp LA back in May.
I'm still very surprised that BitTorrent hasn't pushed more into this space. I mentioned non-infringing uses in January that are a prime example of what P2P distribution enables, and it is even easier with trackerless torrents.
Red Swoosh seems be to rich content delivery what FeedBurner is to syndication. It's not that they necessarily do anything you couldn't do on your own otherwise, but they really simplify the process of delivering peer-to-peer downloads. When run a link through Red Swoosh, it detects that the client supports the Swoosh client and either sends the download link or promps the user to install the client. If there are no supported clients for the platform, it seamlessly forwards to the original URL.
Widespread P2P distribution channels may also be an interesting answer to ensuring network neutrality - that is, rather than relying on the telecoms to ensure open and fair access to the infrastructure, harness the collective bandwidth we are already paying for.