Friendica now has integrated chat in your browser window - similar to Facebook, in fact. An XMPP plugin called jappixmini optionally auto-subscribes to Friendica contacts and auto-approves them. You can add other contacts manually or even configure the addon to integrate Facebook chat buddies. We have a how-to on use and installation of the plugin here: http://friendica.com/node/29
This extension is based on work by the Jappix project.