Crossfire is a multi-player graphical arcade and adventure game made for X. It has certain flavours from other games, especially Gauntlet and the rogue-like games (Nethack, Moria, Angband, and Ragnarok). Any number of players can move around in their own window, finding and using items and battling monsters. They can choose to cooperate or compete in the same world.
GEAS (Group Editing and Authoring System) provides a Web portal for a group of people to work on a set of documents together. It is optimized for RPG communication (campaign background, between-session summaries and details, online gaming) but is useful for any group that needs to manage an evolving collection of shared documents. It supports multiple forums (i.e. campaigns) managed by moderators (i.e. GMs) with a flexible yet intuitive privileges model that enables users (i.e. players) to safely view, add, and edit content. It is based on a MySQL and Perl backend.
u6edit is a world editor for Ultima 6. With u6edit, you can create, modify, and delete objects; manipulate containers, via a tree view; edit terrain in place; view all map and object tiles; view tile and palette animation; view book contents; save map and object data; and play your new worlds with Ultima 6. It is a GTK application written in Perl.
Nethack Records is an on-demand statistics generator for Nethack that is meant to be run on a Web server. It has several types of statistics, ranging from character info to daily and weekly stats. It is implemented with a modern template system, and is very customizable. One can sort by most field-types, such as character class or gender. The code is separated from the XHTML by means of HTML::Template. CSS is utilized to its fullest extent, allowing you to make it look however you like, without knowing Perl.