When the sun doesn't cooperate, you can still "pump up the volume" in Photoshop and save the day. I'm using Photoshop 7 for this example.
The Mayan Indians of southern Mexico built this temple so the sun would shine through this window only two days of the year, during each equinox. After getting up at 4 AM to be in position to get this image, I was disappointed to see a mostly cloudy morning forming, giving the sky more of a soft light effect, reducing contrast. Although the sun came out strong, there was a lot of "wraparound" light.

One of the ways you can improve on a "flat" image like this is by using Photoshop's LEVELS and CURVES controls. First, go to IMAGE>DUPLICATE and make a copy you can work on without hurting your original. Close your original. Then, with your copy open, go to LAYER>NEW ADJUSTMENT LAYER>LEVELS.

You'll see two rows of slider triangles. On the top row of sliders, pull the sliders on the ends toward the middle, by click-and-dragging. Then slide the middle triangle to adjust middle tones.

We get a result like this with better contrast and saturation. It's better, but we can still tweak the color some. Go to LAYER>NEW ADJUSTMENT LAYER>CURVES. Position your cursor over the middle of the diagonal line and tug like so:

Click OK. Then add a layer and go to LAYER>NEW ADJUSTMENT LAYER>CURVES and this time use the menu at the top of the box to select the RED channel. Tweak it like this:

Now we have something we can use.

This effect works to enhance all types of sunrises and sunsets, around palm trees, beach chairs, when we don't have our Cokin filters and the sky just doesn't have the colors like you see in the travel magazines. Speaking of shots like this, usually the sun gives you time to make adjustments (when you're not slapping mosquitos), so shoot horizontal and vertical format shots. You never know when you might get that cover shot, and it better be a vertical!