The Pragmatic Programmers have a very good sense of software developmet trends -- they're doing today what O'Reilly did in the early 90s. Coming in July from them is Joe Armstrong's Programming Erlang. Erlang is seen by programming language mavens as one of the real contenders for the crown of "most practical language for writing concurrent programs." I haven't sensed any real groundswell for Erlang recently, but a great book on the language might well contribute to an uptick in popularity.