How to display Google App Contacts in a separate iChat list?
I actually just tried this and iChat does it automatically. As you can see I have a different window for each account, and I think you can actually set the window's title by setting the account description under Settings-&gt;Accounts. As you can see I even have different groups for each account.  
Although I usually have them unified using Chax's feature Use All Contacts window as primary contact list