Back in the 1990s or so, I had a notebook page filled with nothing but automated phone lines to call. Back in the twin cities, we had "CityLine", where you call it up, punch in a 4-digit number, and you get some prerecorded message about whatever. To me, this was fun to explore. I started trying different combos to see what I'd get.
One time, I found an interactive game to play on it. It was like "hit 4 to go left, 6 to go right". Sounded like something you would get for a 900 number or something. That provided hours of fun as a bored teenager.
The list grew and grew. Another one was "The Connection", which was just like Cityline. Any time I saw some "hotline" to call, it went in the notebook. Most of them were just voicemail lines on announce-only(ie you cant leave a message). Hit a random DMTF tone to see what happened. Most of the time it was a login prompt.
The only one I know of left in the twin cities is the KARE 11 weather hotline. I can only assume the Internet has made yet another thing obsolete.