I'm still working on it but here is what I have right now. Please let me know if you have any problems in the rss reader your using. I've just been testing it in the google rss reader and the Thunderbird reader.
Shows latest interfaces same as front page. (capped on 20)
http://www.wowinterface.com/rss.php?f=latest
Shows only latest NEW interfaces. (capped on 20)
http://www.wowinterface.com/rss.php?f=latest&r=new
Shows only latest UPDATED interfaces (capped on 20)
http://www.wowinterface.com/rss.php?f=latest&r=updated
Author RSS2.0 feed. replace the aid= number with the id of your favorite author. I'll have an interface soon for all these rss feeds so you dont have to edit the url. (no cap)
http://www.wowinterface.com/rss.php?f=author&aid=14234