The Gathering is one of the largest computer parties in the world, with approximately 5200 people attending (the interest is much higher, but limited tickets).  The first "The Gathering" was arranged in 1992, so this is a quite famous computer party. The later year the focus has been more on online gaming than computer demos and programming, which is sad.

If you're attending this years TG be sure to check out my fellow RD Sondre Bjellås presentations on XNA Game Studio and Visual Studio Robotic Studio. You can read more about his plans for the presentation over at his blog.