Well this NRW section was totally empty so I thought it would be nice to add something.
From the 2nd to the 5th of June each year, there is a Music Festival/Camping extravaganza held in Moers (near Duisburg). The event started as a jazz fest but has grown to encompass what could be described as independent and world music. From what I've been told (and from the pictures I've seen) it appears to be like the Tollwood Summer Festival in Munich - only you get to camp there.
For anyone who is interested in going, you can find more info on the following website.
Moers Festival Website