Down in the Alport valley by the river, or in the woodland nearby where there's some flat ground, i've camped there a few times.
Back tor on Derwent Edge, there's a bit of flat ground under the overhanging rocks, myself and Moonlightshadow spent a night there a while back.
There's also loads of options on and around Kinder.
Include a little history in your walks. Pecsaetan - Ancient Derbyshire, Staffordshire and South Yorkshire - http://pecsaetan.weebly.com/