I don't know much about messaging, so I'm not sure whether this questions makes sense or not, or if it's just dumb.

Is there any kind of desktop application that would allow my wife and I to exchange messages between our PC's, so that we don't have to yell up and down the stairs, "HEY! Check out this URL! ..." I know we could do it by just signing up with any of the Instant Messaging services out there, but isn't there something that would just allow us to communicate directly on our LAN, without going out to our ISP and back? I know I used this kind of thing on Unix networks years ago, but I don't know what it would be called in this day and age.

The wrinkle in this is that my wife is currently running WinXP :-( , so it would have to work there, too. If not, though, maybe she's ready to return to the bright side ...

- Bruce

Well, you can install jabberd. On FC4, it's just:

yum -y install jabberd

Any Jabber client (like gaim) can communicate via this open source messaging protocol.