Beadnell Bay CCC campsite, Beadnel: 01665 720586
Springhill Farm campsite, Seahouses: 01665 721820
One walk you mustn't miss - from the mainland at Beal across the sands to Holy Island, following the line of poles. But be sure you find out the tide times and the safe crossing period.
If you have a car you could drive to Wooler and up the Harthope valley to Langlee then walk up The Cheviot, the highest point in Northumberland.