Time to mesh XOs
Unless you're lucky enough to live within mesh range of many other XO users (or are part of an XO deployment or an innovative classroom project, you probably have a pretty empty "neighborhood," and look to Internet jabber servers to connect with other XOs.
The state of the public jabber servers of recent has been in flux for a while, but seems to be settling down.
XOChat.org seems to have disappeared from the Internet (any word on why?), and scouring the OLPC Wiki for community servers has led to more dead ends than I care to relate. To be fair, I've mainly been using Pidgin.im instead of my XO to test the networks out, and some servers, including XO1Share.org, isn't playing nice with my IM client - but does seem to have a decently vibrant community of XO users on it. Jabber.laptop.org and jabber.sugarlabs.org are the other contenders currently (and jabber.laptop.org allows IM clients!, Sugarlabs throttles non-OLPC connections).
There is also a scaling limitation in that any server can only take ~150 concurrent users.