Thanks to an entry on the Liferea FAQ, I now know how to get an RSS feed for any LiveJournal. All it takes is a little URL magic.
Enter the following URL into your feed reader, replacing [username] with the correct username for your friend with the LJ:
http://www.livejournal.com/users/[username]/data/rss
Voila! By way of example, here are feeds for a couple of my friends’ LJ blogs:
Okay guys, now I can honestly promise to do a better job of staying up to date on your weblogs.
Update: Gregory Blake shows how get access to friend-locked LJ posts through your feed reader.