Simula introduced the object-orientedprogramming paradigm and thus can be considered the first object-oriented programming language and a predecessor to Smalltalk, C++, Java, and all modern class-based object-oriented languages. As its name implies, Simula was designed for doing simulations, and the needs of that domain provided the framework for many of the features of object-oriented languages today.
Simula was never just an academic language (it was still used for a few real-world applications as of 2003), but its historical influence is considered far more important than any actual work done with it.
Introduction to OOP in Simula (http://staff.um.edu.mt/jskl1/talk.html) – By J.Sklenar, based on the 1997 seminar "30 Years of Object Oriented Programming (OOP)" at the U. of Malta
How Object-Oriented Programming Started (http://heim.ifi.uio.no/~kristen/FORSKNINGSDOK_MAPPE/F_OO_start.html) – By Dahl and Nygaard, abbrev. version of an encyclopedia article; on Nygaards home page
The language was designed by Dahl, Myhrhaug and Nygaard at the Norwegian Computing Center, Oslo and the first version of the language, Simula-1, described in 1966, was strictly a Simulation language (like GPSS).
In addition to leading to modern Simula, Simula 67 was an inspiration to the Xerox Palo Alto Research Center (PARC) group who developed Smalltalk and to Bjarne Stroustrop in his development of C++.
An Introduction to Programming in Simula (R.J. Pooley)