Arx Libertatis is a cross-platform, open source port of Arx Fatalis, a 2002 first-person role-playing game developed by Arkane Studios. Arx Fatalis features crafting, melee and ranged combat, and a unique casting system where the player draws runes in real time to effect the desired spell. The Arx Libertatis source code is based on the publicly released Arx Fatalis sources. This does however not include the game data, so you need to obtain a copy of the original Arx Fatalis or its demo.
AYUMiS is a project aiming to create a cross-platform MMORPG set in space. It is developed in C++ with ClanLib. It will give the player full control over the game universe, with no NPCs or pre-planned storyline. It attempts to give the player a full range of choices and open-ended gameplay.
OpenMW is an attempt to reimplement the popular role playing game Morrowind. It aims to be a fully playable implementation of the game that will run on Linux, Windows, and Mac OS X. No game data is distributed with the code; the user must already own a copy of Morrowind to use the software.