There are a couple of interesting books that have been released (relatively) recently. Peter van Roy, of Oz language fame, and Seif Haridi have written a book called Concepts, Techniques, and Models of Computer Programming. It's a general-purpose introduction to computer science and programming languages. It emphasizes a "kernel language" approach, where a wide range of programming language features are built up from a small set of carefully chosen primitives. The book also examines different programming language paradigms (functional, object oriented, logic, concurrent) and shows how they can be integrated.

Shriram Krishnamurthi has just this morning released a PDF version of his textbook, Programming Languages: Application and Interpretation. I haven't read it yet, but the book has already been used at Brown as the textbook for a programming languages course, and Shriram is a smart guy with interesting things to say about programming languages, so check it out.