From Selznick Scientific Software:
Program that draws the current phase of the moon in the system tray area, next to the system clock. The moon, when clicked, reveals a textual description of the moon phase, illumination percentage, the moon's age in days, current lunation number, and upcoming quarter predictions. Select an item in this menu to copy the information to the clipboard... then paste it into an e-mail.
MoonMenu is also an application that allows you to investigate all of the lunar data presented above for any date and time.