The effect that a polarizing filter adds to your photos is one that isn't easily, if at all, achievable using post processing software. Because what your polarizer is doing for you is filtering out the effect of light reflecting back from the surfaces it hits. In turn you get more saturated colours and if required, bluer skies. I'm using a Circular Polarizing Filter (CPL) on my DSLR for these examples.
In this example above, the sun is behind me and slightly to my right. Without making any colour tweaks to my files this is what I got using the same settings. The only difference is that I overexposed by 2 stops for the polarized shot to take into account the darkness of my filter. Most of the dark reflections in the water have beed neutralized giving me a much cleaner looking sea and I've also got better definition between the clouds and the sky.
Here I'm shooting with the sun at approximately 90 degrees to my viewpoint. At this angle I can get the maximum effect of my CPL. Again with no colour adjustments, I have more pleasing colour rendition and a darker blue sky. The CPL filters rotate on the front of your lens so you can dial the amount of polarization you want up or down and see immediately what the effect is in your viewfinder.
And this last example is taken from the edge of the beach looking into the water and the result is self explanatory. If you decide to purchase one of these filters to add some punch to your photographs, look for a filter with a low profile. Low profile filters will be less affected by vignetting as the light enters your camera lens.