One program I wrote (in BASIC) when I first started learning programming was an "email server". It wasn't actually a server, and there wasn't actually email. It consisted of a login screen, then some commands, like listing users and their profiles, sending messages to those users, and reading your own messages. It stored everything in text files on a single computer, but it was fun for me and my friends to leave each other messages on a school computer that we all had access to.

Another program I wrote was a chat program. It consisted of a single chat room and private messaging capabilities. This one was also fun to write and a great learning experience.