blinkperl is a telnet server (written in Perl) which plays a random (ASCII-Art) Blinkenlights-Movie if a telnet client connects. In a properly configured system, you do not need a 'usual' telnet server (because of the plaintext password transmission, ssh is better and uses another port), so why not play ASCII-Art Movies on the telnet port?
gtermix is a GTK+ telnet client intended for calling BBSes. It utilizes a custom VGA textmode emulating terminal widget that allows it to accurately render bulletin board systems as they were in DOS terminal programs. It currently features a GTK+ user interface, dialing directory, support for ANSI, vt100, Avatar, and TextFX terminal emulations, and proper rendering for DOS-style BBSes.
This is the old BSD tn3270 made to compile under Linux/GLIBC. It is not perfect and not being actively maintained. Also in the same directory is 3270v4.1 from CERN, made to compile under Linux/GLIBC, which looks nicer. If you are interested in these programs, you may also want to look at the Linux tn5250 project.
Playlist Warlock is a text-based frontend for mpg123 written in Perl. It is intended to provide users with the playlist browsing and song selection of a GUI MP3 player from any terminal. It provides a combination of Winamp/XMMS, vi/less, and Unix prompt-style commands for creating, editing, sorting, and navigating MP3 playlists. Using mpg123 as a backend, PLWarlock allows the user to easily browse playlists and play MP3s. It supports contiguous and random play, simple jump-to-song syntax, sorting by filename/path+filename, and all the other commands you've come to expect from a good MP3 player.
mimic is a server that mimics Internet servers. It includes imitators for ftpd and telnetd, and can be extended with scripting to support other types of imitation. Users will believe they are connected to authentic services (such as ftpd or telnetd) but will never be able to log in. Everything that they type is logged. In addition, scripting new imitator services is simple. The program includes a one-liner example of a fully-functional echo server. The project's goal is to create a script for imitating most, if not all, popular Internet services.