Until such time as someone tries to fill the shoes of Jean Sammet and write a new overview of programming languages (a major job, that!), the HOPL conferences are the main source of insight into the development of programming languages that, Sapir-Whorf style, have shaped the way we view programming and the problems we try to solve with a computer. Even if someone does take up that task, the HOPL conferences are invaluable, since they provide information straight from the people involved.
This volume of the proceedings of HOPL II is thus invaluable for the student of programming. HOPL I covered the main early languages (Algol 60, FORTRAN, COBOL, LISP, APT, BASIC...); HOPL II covers important languages of more recent vintage (Algol 68, Pascal, C, C++. more recent dialects of LISP). C.H. Lindsey's fine paper on the turbulent development of Algol 68, the best language you probably never used and a major influence on later languages, is worth the price of admission by itself.

I have read many many computer jounrals about the history of computing. Very few resources have put the kind of time and effort that Thomas Bergin has done in his book. Along with assistant editor, RIck Gibson, both men do a fine job collecting the best of the best resources and giving it right to the public upfront. I wish Bergin can do another book or something Internet related because this is truly apart of computing that we do not really have much material on.