The line between IM protocols is becoming more and more blurred. Starting today [some] GMail users now have the ability to sign into their AIM account. Looks like only one account (yes, I have a couple). If you don’t have the option yet, you should be getting it in the coming weeks. It doesn’t look like ICQ users show up (AIM can communicate with ICQ as AOL owns both).
The Google Talk desktop client doesn’t support “AIM Talk” yet but I’d suspect we’ll see that very soon.