mod_bt is a BitTorrent tracker running as an Apache module, seemingly set out to integrate seeding at some point. Not to be confused with dormant mod_torrent which seems to have had similar intentions.
BlogTorrent (aka BattleTorrent) is a do-it-yourself PHP/Python tracker. Using its server seeding feature, the web server itself can seed its data on a per-file basis. BlogTorrent also supplies adapted Windows and Mac OS BitTorrent clients.
BitTorrent support for web clients
Opera's 8.02 Technology Preview features native BitTorrent support. It has been pulled in subsequent beta and regular releases, but according to rumors it will be ready very soon.
firepuddle is the officially endorsed plugin for Firefox. Not for the faint at heart, classified as highly experimental, requires latest Firefox beta.
MozTorrent is the original Mozilla integration project, no releases so far.
Peer-to-peer web publishing
These sites publish web content on peer-to-peer networks, partially using BitTorrent.
The Coral Content Distribution Network transparently serves webpages over a global peer-to-peer network. To refer to content using Coral, publishers simply append .nyud.net:8090 to links.
Dijjer allows publishers to seed their files on the Dijjer network (not BitTorrent) by simply prepending them with a special dijjer.org URL. Upon selecting the link, the Dijjer P2P client is activated to retrieve the respective file. If the client is not installed on the user's machine, he is prompted to do so.
Prodigem publishes via BitTorrent and offers advanced features such as RSS enclosures.
Hurricane Electric's BittTorrent hosting service offers seeding and tracking for their customers - they just have to place their files into a special FTP directory. It is based on the internally developed my5minutes.com, which is open to the public.
WebTorrent describes a client-server mechanism to transparently serve packages of HTML pages and their assets (images, stylesheets) via BitTorrent in order to perform load-balancing. Software is unavailable.