Take a horribly washed out shot, like this one that I did the other day. (It was about to rain, but I wanted to remember this place so I could come back and maybe do some stuff another time...)

Open a pic in Photoshop, and then choose Image>Mode>Lab Color from the menu.

Then choose Image>Adjustments>Levels...

Then, while on the Lightness channel, bring  the sliders under the histogram over to meet up with the darkest and lightest parts of your data. (Like this...)  

Now for the cool stuff.... Go to the B channel. Now slide the light and dark sliders about half way in. It WILL start to look horribly wrong, but if you move them both the same amount everything with look normal again!! Then use the middle slider to adjust your pic from bluer to greener. (Like this...)

Now use the A channel for the reds. (Like this...)

The end result may not be perfect with just these steps alone, but it no longer looks like a rainy day in January! (Results...)

Yes, you CAN do the same thing if you use Hue/Saturation in conjunction with Levels and maybe Color Balance, but this seems to be a lot easier that dealing with the 6 sliders in the Hue/Saturation dialog box. Trying to tweak greens, blues, and cyans all seperately?!?!?

Aahhh!!!

Anyway, if this helps anybody out there, then my job is done.