AOL Instant Messenger has been my main resource of internet communications for almost two decades.  On December 15th, 2017 AOL will be shutting down its AIM services for good.
Earlier this year they disabled 3rd party services from using AIM at which point myself and most of my friends had our last conversation using this legendary service.
As for alternatives, chat applications seem to be a new hit thing in the last few years. It seems that ICQ is still available if you want to feel nostalgic and see what old friends may still be using that client. You can also still use clients like IRC (Internet Relay Chat), Discord, Google Hangouts (until google eventually kills it), Slack, Hipchat and I’m sure there are a few others around that should be recommended.
From their announcement:
Why is AIM shutting down?
“We know there are so many loyal fans who have used AIM for decades; and we loved working and building the first chat app of its kind since 1997. Our focus will always be on providing the kind of innovative experiences consumers want. We’re more excited than ever to focus on building the next generation of iconic brands and life-changing products.”