When it comes to map mashups, there's no doubt that Google Maps leads the way. On ProgrammableWeb we list 1,971 Google Maps mashups, almost four times as many as any other API. This popularity makes utilities built on top of Google Maps especially interesting, such as this contextual menu control, which pops up a menu when the user right clicks.
Wolfgang Pichler, who wrote the control, explains how it can be used:
The result is a control that's easy for users and easy for developers, and is probably the fastest way to add reverse geocoding and directions functionality to your map (especially if it's a small map). Just include the script tag for the source code, insert [one] line in your map init function, and you'll get a right-click menu
The documentation includes examples that show how to exclude specific items from the menu. Unfortunately, there is no means to add your own items to the menu. However, with the control being open source, enterprising developers could add this functionality.