These I used myself (Score 1)

Being a hardware engineer my self some books I have been reading from time to time are

VHDL:
Pong P.Chu - RTL Hardware design using VHDL (2007)
Volnei A. Pedroni - Circuit Design with VHDL (2004)
One of the following is really good for VHDL but I don't remember which of the two I keep confusing them...
VHDL Handbook by HARDI electronics (1997)
Peter J. Ashenden - VHDL Cookbook (1990)

U. Meyer-Baese - Digital Signal Processing With FPGA (2007)
Laung-Terng Wang, Cheng-Wen Wu, Xiaoqing Wen - VLSI Test principles and architectures (2006)
Jean Pierre Deschamps, Gery Jean Antoine Bioul, Gustavo D.Sutter - Synthesis of arithmetic Circuits (2006)
Michael Keating, Pierre Bricaud - Reuse Methodology manual for System-On-Chip designs (2002) - Must have for HW design
There are also books like Patterson's Computer Architecture which are really fundamental.

For the state of the art you can search for papers in IEEE explore and ACM portal as well as Springer books there are some gems there!

Hope that helps.