I've finally figured out how some photographs look simply fabulous, like the ones by pro photographers that always win Canadian Geographics’ annual photo contest. They pump up the saturation.
Saturation is the intensity of colors. More saturation and the colors are more intense; less, and the photograph begins to look like a black-white photo.
Your camera might have a saturation settings. On my Canon S1is, it is found in the Func. menu. Move down to Custom Effect, press Set, and then change Saturation. This camera offers only three settings: more, normal, or less.
My other camera, the Samsung NV3, handles saturation differently. Press the + button, and the press the four-way controller until you get to the Red-Green-Blue setting. Now increase each one by a few steps.
Take some photos, and suddenly they no longer seem so bland looking.
If you don't want to contaminate the "original" photos with the camera's saturation settings, you can post-fix them. For example, Picasa has a saturation setting that lets you see the effect in real time. Notice that when the saturation is too strong, colors start to look wrong, and black areas can get flooded with electric blue.
Saturation is like salt: a little enhances your photos, but too much kills them.