Can't advise you on digital filters I'm afraid - I don't have any for my camera. However, the V. expensive optical-digital cameras may well be able to use filters.
My SLR camera, on the other hand, has a skylight 1A fitted permanently - on the advice of a professional photographer friend. He says it doesn't do a scrap of good it filter terms, but it is a cheap and effective way of protecting a very expensive lens face.
Polarising filters give enhanced blue sky effects, and are especially effective in taking water shots in bright reflective conditions. I once photographed some swans at close range from a boat, looking almost straight down; when the prints were processed, the swans appeared to be floating in mid-air and fish were clearly seen below them - more by mistake rather that good judgement, the polarising filter completely removed all trace of the surface of the water and there was sufficient light to illuminate the fish.
Unfortuneately, the Schlieren effect is triggered by gold film heating, hence the wierd patterns you get with polarising filters and sunglasses.