I have personal plans to develop my own sort of “trn for the web”; specifically, software which

• takes as input: RSS/Atom feeds, possibly NNTP (Usenet) and email, as well as custom adapters for sources like LW which rely on threading but do not export it in common machine-readable form;
• is used as a web-application but can be on one's own computer or a multiuser server;
• provides UI features: efficient stepping through messages, easy thread-tree navigation (probably very similar to trn), and remembering read messages.

However, I have no code as yet and no timeline; I might start working on it this summer or fall. I don't imagine anyone wants to help out under the constraint that I make all the platform and design choices...