A couple other people and I have been working on a game called DMUX over the last few months (it's been slow progress) using Irrlicht and Bullet (among other APIs). We are currently hoping to recruit new people for our project. Be aware that we are strictly using Free Software and the game will be licensed with the GNU GPLv3 for the client and GNU AGPLv3 for the server.
The concept of the game is a 3D derby-style shooter, I've heard that the concept is a lot like that of Twisted Metal. We'll be having two (or more) teams hosted on a server that play against each other with a 'third-party' AI of Zombies that will be used to even out gameplay between the players (to make sure that if a single team has all of the good players, the game is still fun for those who aren't as good). The networking dynamics will have a client, server, and master server, similar to the design of Xonotic or AssaultCube (for networking we're using SFML).
If you're interested in joining us, contact Brigham Keys at <email@example.com>.
We also have some videos of what we have so far which can be found at the following link (please take into account we haven't implemented Bullet Physics yet):