I wanted to place these photos right next to each other so you had a reel feel for the results. Not all polarizers give the same results. I would suggest you do a little research before you purchase but they do add a ton of possibilities to your photography.
The polarizing filter used for this test is a HOYA HMC, Multicoated CIR-Polarizing 77mm Filter. Lens is a Nikon 17-55mm, f2.8. Camera is a Nikon D90. Photos shot is Shutter Priority with a 17mm focal length. Time gap between the two photo is 5 secs. Photo A - f13 @ 1/200 sec, iso 500. Skylight Filter only. Photo B - f10 @ 1/200 sec, iso 500. HOYA HMC, Multicolored CIR-Polarizing Filter.
Now if you wish to see the real results. Copy a big size version on to your desk top and toggle between the two photos. The sky and cloud details that are viewable in the polarized version are incredible. The price for this filter ranges from $80 - $120. They aren't cheap but I do enjoy the added color benefit. I have enjoyed having these filters in almost every situation but especially in deserts and high sun situations.
Hope that helps.