Really Simple Sharing
Ray Ozzie does it again: he's proposed (under a CC license, no less) a new standard that leverages RSS to allow multi-master sharing of the info that you need replicated, with appropriate filters. As an example, think of having all of your calendars (private, public, home, work, shared with spouse, shared with study group) managed through one interface, with the updates only going where you want them to go, thus keeping your worlds as separate or as together as you want them to be. And this applies to your contacts, your files, any list you have anywhere of stuff that needs to be replicated elsewhere.
Ray has a blog: only two items so far, but it will be one to watch.