Practical Foundations for Programming Languages by Bob Harper is really good, plus there's a free draft of the second version on the author's site http://www.cs.cmu.edu/~rwh/pfpl.html
I always go to the book author's page first not only to get the errata but also discover things such as free lectures as in the case with Skeina's Algorithm Design Book
I always go to the book author's page first not only to get the errata but also discover things such as free lectures as in the case with Skeina's Algorithm Design Book