This article talks about tools which are helpful to find the enhancements in your current sap system or in a particular transaction code.
This article contains bird view of all the new enhancement Frame work and Switch Frame work also the Tutorial on Implicit Enahancement.
This Articles contains the Example with explanation which will help you to understand Function module EXIT and how to work with it.
Check this article to know how SCREEN EXIT works.It also contains the example of SCREEN EXIT with screen shots.
Check this beautiful article to know everything about USEREXIT. It also contains tutorial of how to implement a User EXIT.
