Oban has two main campsites,
http://www.obancaravanpark.com/ and
http://www.roseviewoban.co.uk/ , they`re use to be one at Ganavan sands but i think not there anymore, due to redevelopment of the area (Ruined it). Plently places to just wild camp, just find a green patch
. Loch Etive via Bonawe side past the quarry is good place for wildcamping, you have a couple bothy`s up there too if weather gets too extream. I`m still on search for ideal place for myself to get away from real life, i`ll find it someday lol