Formal Semantics of Programming Languages I'm new to programming languages theory and I'm seeking for a good resource on a resource for formal semantics  of programming languages. Specifically looking  for structural operational semantics. I got some book recommendations. But I'm looking for a resource in a  more introductory level. Especially tutorials, web-site and free book recommendations are  welcomed.
Looking at the operational semantics course at my University gives the following three:


Andrew Pitts's lecture notes
Gordon Plotkin's Aarhus notes on structural operational semantics
Matthew Hennessey's The Semantics of Programming Languages


Ohad.