AdesClrPicker is an easy to use standalone program that let's you designers out there easily get the code for colors anywhere on your desktop.
Of course it you're using firefox there's an extension out there that does the same thing but that will only let you pick colors from your browser and Ades Color Picker has some useful extra features built in.
AdesClrPicker has a color library that let's you manager the captured color codes, you can delete and edit colors ( set up the RGB values ), you can save the codes in a text file different formats ready to be used in HTML, Delphi, C++ and VB.
When started, this program goes to system tray and waits for activation.A right click on it's icon in system tray will show a popup menu with several options (Activate, color Library, Settings, etc ) and a list or recently captured colors.
You can activate it from that menu or with a key combination that you can customize from settings.
Flexible and easy to use, no need for photoshop loaded just for picking colors, not that I use photoshop, gimp rocks at least for my image processing needs.
And btw this color picker almost works in Linux if you have wine. I say almost because you can start it but it will only pick colors that are inside it's own window, but this is because of a problem with wine applications not being well integrated into the X window manager. Maybe a future version will have Linux/Unix support too.
Here are some screen shots of the color picker in action:
What color picker and design tools do you use for web/software development? I would love to hear about them in the comments.