you can use psi (or whatever software you used to register with Jabber) to add an AIM gateway to your jabber account, provided your jabber server offers one.
Your AIM contacts will show up in jabber then.
This is flaky, though, and contacts will not show up reliably for me.
Also, AIM via Jabber doesn't appear to support video or audio - at least via jabber.ccc.de (my chosen jabber server).
-s*