Xanga Posts sent to LiveJournal:
Simple. I'll need 1 account that will subscribe to people who will opt-in (somehow...) to have their entries sent to livejournal.
Xanga has their own form of "friends recent entries" page, sent in the form of an e-mail. This will arrive at some mailbox somewhere on my computer, be deciphered, then posted in the form of a livejournal entry, probably under lj-cut tags.
Problem: No control over at the livejournal side as to who's entry you want to view. It's all or nothing. Also, these will be viewable to the public, most likely.
LiveJournal Posts sent to Xanga:
Crontab scripts run once or twice a day. They'll connect to livejournal, use the friends page to grab the entries since a certain date (oh, this might be kinda hard. Date time parsing...) and post to xanga as a large chunk.
Problems: large entries, without a doubt. Also, lj-cuts will have to be handled separately...
It's an interesting idea, actually. Probably can't handle more than 20-30 people though, unless we do separate entry per post copy over. But that would look ugly on both liveJournal and Xanga.
Oh, and there aren't any threaded comments for Xanga. Stupid much.