I agree with the others that fill flash is the only way to bring the above shot into "balance" -- sometimes the blown background is OK, sometimes not, but if you want to avoid it fill flash is the way.
Circular polarizers can bring your whole exposure down a bit but their main purpose is to bring some highlights down a bit, and they can lend a saturation effect to some colors, such as a blue sky, but the effect is dependent on the direction of the sun and also they won't do anything for that particular image.
Neutral Density Filters are meant to lower the exposure for a given shutter/aperture/ISO setting. They can be useful for specific things, such as allowing a slow shutter speed to show "motion" in moving water or with pedestrians or moving vehicles, without sacrificing other elements to keep the scene from being overexposed. Again, no use in your photo above.
Graduated Neutral Density filters darken a portion of the screen then gradually lighten until there is no darkening (full exposure). This can be useful with say a landscape scene with a foreground that you want to "properly" expose but a bright sky that you want to keep from blowing (as would happen if you properly expose for the foreground. If used properly GND filters can be very effective, but realize that you will have to deal with features on the horizon level that may come out poorly with that type of filter. Now, the shot you show has a similar challenge (bright sky) but the composition would not be helped by a GND.
Filters can have a use even in the digital world, but something to bear in mind is that giving in to the temptation to buy "cheap" filters is a big mistake. Inexpensive Neutral Density filters, for example, often have an undesirable color tint to them. Cheap UV ("protection") filters tend to cause glare -- so much so that many people just don't use them unless really bad conditions warrant them.
Hope this helps some!