Game development on Linux has always been behind due to a variety of reasons. However in recent years the newer generations demands the ability to edit, manipulate, and add content to their games. Homebrew’s are huge now and many are more interested in game development than game playing. One website/repository stands out for Ubuntu/Linux. PlayDeb is an amazing collection of quality open source games. Many are extremely addictive and contain some exciting editing tools within. Syntensity is an amazing new game boasting the open source engine Intensity. The SandBoxGameMaker by Platinum Arts contains a suit of tools for game creation. There are a variety of new and old games created originally from the Sauerbraten game engine. Take a look at PlayDeb and make sure to add their repository to your Ubuntu box and start gaming.
Just to clarify, Playdeb is a complementation to the game software you already see in the Ubuntu Software Centre – it only lists games that aren’t on USC, or are outdated.