G.D. Plotkin. A structural approach to operational semantics. Technical Report DAIMI 19, Department of Computer Science, University of Aarhus, Denmark, 1981.

A more mathematical (and therefore harder to read account) is in:

Daniele Turi and Gordon Plotkin. Towards a mathematical operational semantics. In Proceedings, Twelth Annual IEEE Symposium on Logic in Computer Science, pages 280-291, Warsaw, Poland, 29 June-2 July 1997. IEEE Computer Society Press.

A historical overview is coming out soon.

Kahn's version of Plotkin's work is in:

G. Kahn, Natural semantics, 4th Annual Symposium on Theoretical Aspects of Computer Sciences on STACS 87, p.22-39, February 1987, Passau, Germany

Text books that contain sections on this style of operational semantics are:

Slonneger, K. and Kurtz, B. Formal Syntax and Semantics of Programming Languages. Addison-Wesley Publishing Co. - Reading, Mass. 1995. A good overview that takes a middle road between theory and practice.

G. Winskel. Formal Semantics of Programming Languages. MIT Press, Cambridge, 1993. An extremely thorough account, very formal and rather tough to read.

You can also find many useful web sites for various professors across the globe. If you need help with any of this, let me know.