weblogs.com maintains an automatic list of recently updated journals and weblogs as a resource for people looking for new sites to read. In order to have your journal included in this list, you must send a message, or ping, to weblogs.com when it has been updated. To have LiveJournal notify weblogs.com when your journal has been updated with a public entry you can select the "Notify Weblogs.com of updates" option at http://www.livejournal.com/editinfo.bml
N.B. that's the first time I've ever tried to write an FAQ so that's very much a first draft for discussion.