It was common practice at Mayflower marina to berth to a couple of old tyres attached by short chain to the pontoon at bow and stern. The weight and flexibility meant there were no snatch loads, and so no creaking. There are rubber thingies that you wrap your warp around which will do the same job when away from your berth. The cheapest (but slightly hassly) option is very thick bungee cord and a couple of running hitches to leave a small hanging loop in your warp with the strain taken by the unstretched bungee.
I have used washing up liquid for squeeky fenders with some success, unless its raining, of course.
Out here you can buy rubber spring things that you thread the ropes through. (I'm sure they have a more technical name) They give extra spring and do help a bit.