<a href="http://www.peuplade.fr>; Peuplade</a> is a site in France for organizing social activities around your geographical location. It's great to meet people in your neighborhood! I found it an excellent opposite to Facebook, which keeps you in touch with people far away (that was my original perception, at least).
I find the "neighborhood" approach much more interesting for a social site than "real-life friends". Another interesting use of social networks is <a href="http://www.couchsurfing.com>CouchSurfing</a>;
I read an article about that study a while ago. Maybe it was this specific article, as it dates back to June 2009. I found it extremely interesting in that what our western culture considers "success" doesn't necessarily lead to happiness. It has vindicated me in finding balance in my life and not investing too much of it just in my job.
I'd like to do something like this when I have kids. However I'm afraid that it's just a reflex against the way I was brought up, way too sheltered and forced to go through school and ignore my real interests. I would just be projecting on my kids what I would've wanted for myself, and that's not good.
Actually, from talking with the OneSocialWeb [1] and BuddyCloud [2] guys, I understood that Android phones have a really sophisticated "always connected" philosophy. The main CPU can go into deep sleep and the phone still maintains a persistent data connection, waking up the CPU on incoming data. That's for the low-level IP stuff. TCP-over-GSM really sucks your battery.
XMPP doesn't (yet) have a standardized way of filtering data. Using Privacy Lists is a workable hack. Google implemented their own thing (using Protocol Buffers [3] to replace XML-on-the-wire, instead of gzipping as the XSF recommends). Process One has their own system as well for OneTeam [4].
The future ideal is to use SIFT [5], but it is still experimental and as far as I know, only Prosody [6] has partially implemented it.
Thuderbird has a pretty good calendering extension called Lightning. By default it adds a pane to the normal view with upcoming events: "Today", "Tomorrow", and "Soon" for stuff in the following week. I find that tremendously useful, and close to Marco's idea.
I find the "neighborhood" approach much more interesting for a social site than "real-life friends". Another interesting use of social networks is <a href="http://www.couchsurfing.com>CouchSurfing</a>;