1. Single Responsibility

http://en.wikipedia.org/wiki/Single_responsibility_principle (ToRead)

2. Open/Closed

http://en.wikipedia.org/wiki/Open/closed_principle

3. Liskov Substitution

http://en.wikipedia.org/wiki/Liskov_substitution_principle  (ToRead)

4. Interface Segregation 

http://en.wikipedia.org/wiki/Interface_segregation_principle

5. Dependency Inversion

http://en.wikipedia.org/wiki/Dependency_inversion_principle

Plug-in

http://en.wikipedia.org/wiki/Plug-in_(computing)