The Source for Information on Developing a Scripting Host:
Active Scripting FAQ

A serie of article on Active Scripting by Eric Lippert:
Simple Script Engine

Cropper is a screen capture utility written in C# on the Microsoft .Net platform. It makes it fast and easy to grab parts of your screen.

Download Cropper

I found an interesting article about Ecommerce Providers here:
Ecommerce Providers

You may want to check the providers directly:
Avanquest
RegNow
DigitalRiver
Esellerate

It is sometimes necessary to retrieve the position of the cursor within a child control (i.e. TreeView, ListView, etc.)

GetMessagePos will return the position of the cursor when the message was added to the message queue. GetCursorPos will return the current position of the cursor (that can have changed since the message was handled by the application.)

It is better to use GetMessagePos as it will improve how the application reacts to the user action (particularly handling the right-click button.)