For those of you who don't, it's the spiffiest journal archiver EVER. As it modestly says of itself: ljArchive is a tool for downloading, browsing, and analyzing journal entries and comments from LiveJournal (or LiveJournal clones).
Not only does it archive personal journals, as of this release it will also archive LJ communities. This is something that I've been asking for (nay, begging) for ages. I can't get it to work completely on communities of which I'm not the Moderator (it'll download entries, but not userpics or comments, for some bizarre reason) but it's better than a poke in the eye with a sharp stick. I'll be prodding them for an explanation or a fix shortly.
Have fun, save your scribblings for posteriority.
ETA: There's also ljarchive.