xanga blogrings the blogging communityWhich popular blogging service allows its community to interact with that of other services?

e.g., can Livejournal blogs join Xanga blogriings?

Are independently deployed wordpress sites connected to xanga blogrings the blogging communitythe larger wordpress community, including wordpress.com? and can wordpress blogs join "blogrings"/&quoxanga blogrings the blogging communityt;groups" of other services?
wordpress.com allows rss feeds to be syndicated. also many other advantages