LiveJournal RSS Tag Syndication
Basically, it allows you to make an RSS feed for any particular set of tags on any journal. I haven’t tested it much, but it seems to work well for me. It’s also not very documented, but it should make sense to most people, I think.
I hope this doesn’t kill my little server in a flurry of digg-like madness. :-)
The script is written in perl, and I’d be happy to make it publicly available if anybody wants it.