Jeff Segars pointed out a nice little application to me called xScope. It is a collection of utilities that allow you to get information about things on your computer screen.  Among those utilities are:

• Frame overlays to show the cropping of various screen resolutions
• Ways to view and copy the color values of items.
• On-screen rulers
• Methods to measure distances and dimensions of items on screen.
• A loupe to make it easier to read values of individual pixels.

I have particularly found this application helpful in my front-end coding.

Keep in mind that if you want to use xScope to capture accurately the color values within a Photoshop document you will need to do the following in Photoshop:

• set View->Proof Setup to "Monitor RGB"
• activate View->Proof Colors.

Failure  to do so will cause Xscope to read to color values which PS has biased according what is entered in its "Color Settings" dialog box.