There were a couple of things you could telnet into, like library catalogs.
There was also archie for finding files on remote ftp servers. Here's how it worked: anonymous ftp sites would run a ls -lR regularly and put the result in their top-level directory. The archie system would go around and collect these ls -lR dumps. When you typed archie foo, it would find any anonymous ftp sites that had files containing "foo" in their name.
Remarkably this is very similar to how Napster worked seven years later.