Flock sounds interesting: a social web browser. Unfortunately it’s on a private beta at the moment, but features apparently include a wysiwyg editor for posting to weblogs , built-in social bookmarking a la del.icio.us, and a bunch of other features as this review reveals:
But it rocks. Setup was very easy (I tested it with my personal blog). It has functionality for editing posts (even posts not created with Flock), quick toggle between preview and viewing the actual code, and, the best feature in my opinion, the ability to simply drag flickr photos direclty into the post and manipulate them. They also allow quick and easy technorati tagging. Wow. I mean, really, wow. This stuff is not trivial to build. The ajax funtionality is stunning.
I’d really like to see it, not least because I’d like to get it working with Elgg (it’s based on Mozilla so some kind of plugin for extra functionality should be possible). If anyone’s at liberty to knock me an invite code .. nudge nudge ..
 Elgg will, naturally, have a wysiwyg editor very soon