Answers

There is Google Talk, Yahoo Chat, Skype, MSN--there are a lot of services. I would highly recommend trying Trillian, which is an instant message programming that offers interoperability across all the major instant chat services.

Here's a link to the program: http://www.ceruleanstudios.com/

I'd say there is a dropoff in AIM usage once you get to college. I'm not sure why. I imagine it has to do with either less time to procrastinate in college (highly unlikely), less time to sit at home and AIM when you could be out having fun or partying, or just people merely outgrowing AIM.

That said, AIM is still used. I talk to a bunch of college friends quite frequently on it.

MSN is bigger around the world than AIM, especially in South Korea.

I still use it everyday. I don't talk to my HS buddies as much any more though.