Anothertechnique I found while surfing around, trying to find new ways of sprucing up some of my vacation photos from this summer.
This one is a snapshot of an old church in Boston (right around the corner from the original Cheers, if you're interested) and the hazy sky didn't really do much for it. The technique here really makes the blue pop out of the haze, and adds a bit of depth and contrast to the shadow areas.
*Note that it requires Handy Actions, or an action that will select just the highlights of your image and place them on a new layer.
The image to the right is split, with the original photo showing on the left and the effect showing to the right. Check out those rich blue Boston skies!