Eli Bendersky's website I used VHDL on a beginner's level a couple of years ago. Now, when I have to work with it a lot on a high level, it was obvious that I need a VHDL refresher.
I was immmediately handed the ubiquitous (as it seems) "VHDL" by D. Perry. That book is BAD, BAD, BAD. Not only you can't really learn from it, but it is also a poor reference.
Seeking for other solutions I took "The designer's guide to VHDL" from a collegue. After a couple of days of skimming through the book and trying some examples, I was convinced it is the guide & reference I was looking for. I continued reading, diving into more and more advanced topics and my opinion only got better - the book is very comprehensive, also being light-style and understandable. The topics are organized logically (unlike in Perry's book), and the index is terrific - finding topics is easy and painless. What's very important is that the book discusses design methodologies, common techniques used by the experts and (very important) testing. It has a few fully-developed test-cases that together cover high-level design very well. If you follow the whole book closely, you can eventually build its main case-study - the DLX processor from the monumental "Computer architecture - a quantitative approach".
This is definitely the book to get if you have to write designs in VHDL. I ordered it and should have my own copy on the desk in a couple of weeks (company bureaucracy). Can't wait for it...