Not, 'how to take an rss feed and bring it into livejournal.' This question is on behalf of a website I read, really. I asked them, excitedly, if they had an .rss feed ... and they blinked at me and said, effectively, "No, but that sounds really cool. How do we do it?"
Google has failed me (or maybe I didn't use the right keywords), as all I can turn up are actual feeds, not a nice how-to geared at people who don't program in Perl for fun in their spare time.