Smalltalk is a pure object-oriented language, simple and uniform. Smalltalk influenced most of the modern object-oriented languages, although most of the time they missed Smalltalk's elegance and simplicity.
The syntax of Smalltalk fits into one postcard and the object model is simple:
Here is an example of Smalltalk (using Squeak's Morphic GUI classes) that creates an ellipse, changes its color to blue and shows it on the screen:
EllipseMorph new color: Color blue; openInWorld.
You can find more information on Smalltalk at Documentation
Other Smalltalk Implementations
Smalltalk Implementations listed on smalltalk.org
Smalltalk Implementations listed in Wikipedia
Smalltalk Implementations listed in Google's Directory