The Thermarest RidgeRest Classic is one, if not the best value for money closed cell foam mattresses on the market. This is an ideal choice for summer months camping where insulation is not a massive issue. In saying that the Classic still has the peaks and valley ridges that trap air and provide warmth.
Made from ultra durable polyethylene the Classic will serve you well. This is a great choice when you know the mat is going to get trashed on an Alpine ascent or if you're restricted to a budget yet still require a degree of comfort and warmth.