Actually, you can connect to AIM using iChat... it's built-in! But you'll need to setup your own AIM account first (free) at
Instant Messenger - AIM - Instant Message Your Online Buddies for Free - AIM
Then go to iChat > Preferences > Accounts, click the + button, choose AIM Account as the type, enter your AIM screen name and password. Voila!
You can also sign in with your Google Talk account.
Now if you want to connect to WLM, AIM, etc.... it IS possible, but it's not easy. You first have to "connect" your WLM, Yahoo and other accounts to your Google Talk account. Then you can sign in via Google Talk and you'll see the other accounts.
It involves a fair amount of trickery to get it all working, but it can be done.
This topic will give you an overview of the process:
http://www.bigblueball.com/forums/ge...msn-yahoo.html
One of our guests recently posted step-by-step instructions for connecting iChat to WLM (MSN) on his blog:
Passions Just Like Mine: Use iChat with GTalk and MSN Messenger Contacts
Between the two posts, you should be set. Let us know how it goes!