Google Summer of Code 2009 involves numerous projects related to Gnome Games which will involve very experimental new features (networking with Telepathy, 2.5D games with Clutter, and so on). This team's PPA will provide an easy way to install the latest bits from Gnome Games git, including dependencies (Clutter, Seed, WebKit, etc.). Keep in mind that these bits may break at any time, so you're taking your install of Gnome Games into your own hands when adding this repository to your system.