For me it was the Laurel high school system back in 1988-90...it was the public school's computer system for Prince George's County, Maryland and they would leave it up 24/7. This was really before the internet took off in it's current form. It was like a giant party line, teenagers from all over the county would be on talking to each other real time. And then there was a basic email program that you could leave messages for each other if someone wasn't online. I would dial in via my Commodore 64 with a 300 baud modem...it was all text based.