... but it's going to require a linux box on the outside...

Well that's not a likely solution. Anyhoo, I've done some general research on the web and have found many forums where people have asked just this question. It basically comes down to this: AIM is not NAT friendly. There is a beta version currently out which supposedly solves this problem (linked earlier in this thread), but there are no guarantees.

So basically, anyone who wants to use AIM features like Talk, IM Images, or File Transfer and is behind a Linksys or similar router simply has to wait. Assuming, of course, that the current beta version doesn't do the job for them. My sister is unwilling to run a beta version of any software. So she waits.

Thanks for the help, guys.