Information about this music and food festival in German is here.
It's known as the Bean Quarter Festival (due to its location in the so-called Bean Quarter). It's only on for two days : Friday 18.Jul.2008 and Saturday 19.Jul.2008. It runs from 11am until midnight.
Some English info about the Bean Quarter.
It's in central Stuttgart, around here.
Is anyone interested? It's meant to be quite lively, with loads of music provided by both live bands and DJs.