You may have caught on by now that Photoshop has "opposite" blend modes: Darken vs. Lighten, Multiply vs. Screen, and Color or Linear Burn vs. Color or Linear Dodge. So the definition in Photoshop Help for Color Dodge may sound eerily familiar: Color Dodge: Looks at the color information in each channel and brightens the base color to reflect the blend color by decreasing the contrast. Blending with black produces no change.
Similar to Screen, Color Dodge will always result in a lighter image - except the contrast will be turned waaaay up. Here's what it looks like:
I'll start with my standard rose picture:
Then I'll add my semi-standard paw print layer and set it to Color Dodge:
The pure black area of the paw print layer results in no change, but all other areas dramatically lighten the image underneath.
So I have to admit that Color Dodge mode is one that I've never used in an actual application before. But apparently a few other people in Google-world have used Color Dodge mode for lots of different purposes. A lot of people will use Color Dodge layers when making high-tech or grunge-style abstract images. But there were two other suggestions that I found interesting...
More Tutorials: 
