GLEED2D (Generic LEvel EDitor 2D) is a general purpose, non tile-based Level Editor for 2D games of any genre that allows arbitrary placement of textures and other primitive items in 2D space. Custom Properties can be added to the items in order to represent game-logic-specific data/events/associations between items etc. It saves its level data in pure XML files which can be used by any game development library/platform/language.
Check the video tutorials below to get an idea of its powerful features.
GLEED2D is free software and is written in C# and XNA Game Studio.

Build your own AR simulation with the STEP AR editor and Pocket PC client. The Beta version 5.2 of the AR toolkit is now available free of charge for educational, non-profit purposes. The .zip file (10 MB) contains software for your GPS-enabled Windows Mobile PDA, a Windows desktop AR Editor to create or modify AR games, and documentation.

Welcome to Sarien.net, the portal for reliving the classic Sierra On-Line adventure games. With its focus on instant fun and a unique multiplayer experience, Sarien.net hopes to win new gamers' hearts and promote the adventure game genre.

Welcome on libtcod, aka "The Doryen Library" official website.
libtcod is a free, fast, portable and uncomplicated API for roguelike developpers providing an advanced true color console emulator, input, and lots of other utilities frequently used in roguelikes.

The PCG Wiki is a central knowledge-base for everything related to Procedural Content Generation, as well as a detailed directory of games using Procedural Content Generation

This library is a thin c# wrapper around BSD licensed libtcod. It provides a cross platform graphics and roguelike library to those who wish to program in c#

Data generated as a side effect of game play also solves computational problems and trains AI algorithms.

ScummC is a set of tools to create SCUMM adventure games, allowing to create 100% free games that run on the popular ScummVM engine.

The ScummC suite comprises editors and compilers to combine images, costumes, background boxes, fonts, sounds and game code to complete adventure games.

ScummC takes a developer's approach: most of the tools are commandline-based, the build process uses UNIX makefiles, source files are plain text, and the ScummC programming language is modeled after C (hence the name).