There are lots. Fido is still happening and there is an active community. You can see my (very stale) link at the bottom of this post and find lots of boards which you can call right now! Interestingly there are more modern versions running in the east. A very famous Taiwanese one called PTT has 1.5 million users and gets 150,000 users online during peak hours. That's a long shot from the little boards that people run out of their homes, but those are still popular using telnet. What is almost gone is the dialup ones, although there's still enough to keep you busy. Have fun!