Alan Kay is best known for his early work on object-oriented programming using the Smalltalk language which resulted in his Dynabook concept. His concept has never been fully implemented although a modern tablet PC running Squeak comes close. He is one of the core team that produced Squeak and he has also created another Smalltalk based project in 3 dimensions, Croquet. He has also done work in constructionist education.
This book chapter on Personal Dynamic Media shows what Alan was working on in 1977.
More info here: http://en.wikipedia.org/wiki/Alan_Kay