The Global Game Jam is the world's largest weekend game jam, at hundreds of sites around the world! Think of it as a hackathon focused on game development. It is the growth of an idea that in today’s heavily connected world, we could come together, be creative, share experiences and express ourselves in a multitude of ways using video games – it is very universal. The weekend stirs a global creative buzz in games, while at the same time exploring the process of development, be it programming, iterative design, narrative exploration or artistic expression. It is all condensed into a 48 hour development cycle. The GGJ encourages people with all kinds of backgrounds to participate and contribute to this global spread of game development and creativity.
The following link- lists all the sites!