So XMPP is the closest thing to an IM protocol that doesn’t suck. I’ve never read the protocol or tried to implement it, nor do I really want to, but it’s better than all the others. It is better because it’s a real, open standard, and not controlled by any one group, organization, or (most importantly) company. I don’t have to worry about a massive media conglomerate (which shall remain nameless for this paragraph) breaking the protocol my IM client uses so I have to use their client — which is proprietary, and only available in binary form, which makes it simultaneously buggier than most anything else on my system, difficult to find a version for my particular flavor of Linux, and impossible to fix if I find problems in it.
Unfortunately for me, my whole family has gone the evil corporate route of AOL/TW for their IM’ing, including my brother in El Salvador and parents in North Carolina. Since the political party curently in charge of El Salvador these days is the same one that was running death squads and murdering missionaries in the 1980s, and the president of El Salvador said today that if CAFTA (single file) doesn’t pass the U.S. Congress when it comes up for a vote this month, “Central America could return to the instability of the 1980s,” keeping up with the fam is pretty important to me. Important enough to be forced to use an IM client that supports AIM, even though I much prefer Gossip‘s simple, HIG-compliant interface.
(Naturally, I spotted the comments by El Salvador’s President on the CNN crawl while taking a break from cramming for a final in one of my classes later tonight. I almost believe that God has a problem with me getting a degree.)
James Cape 
Please don’t talk about my country as if you know what’s going on.
Have you looked into Jabber transports? I use jaim.at’s AIM transport and it works great for basic chat.
I don’t think Gossip supports gateway registration, but if you log into your Jabber account from GAIM* and register from there it will work fine in Gossip.
After you’re registered with a gateway, just add you family’s AIM screenames as “aim-screename@aim.jaim.at”.
* I’m not sure if GAIM supports this either. I don’t remember how I registered.
What about using ICQ/AIM/MSN/whatever transports? Almost any public Jabber/XMPP server out there has at least some of them installed. And if not you could always run your own Jabber server with transports. And so Gossip will be able to communicate with ICQ/AIM/… users
What’s wrong with gaim? I’m currently using it to connect to AIM, MSN, Yahoo!, Sametime and occasionally IRC. It also does Napster, Gadu Gadu, GroupWise and Jabber.
Gossip works fine with AIM (ICQ and MSN). It just requires a transport on the server (or on a connected server).
Perhaps could you use a Jabber gateway ?
I maintain the fritalk.com Jabber server and my users seem happy with the aim2.fritalk.com gateway.
(First time I see an anarchist putting a capital letter to “God” 😉 )