
Introduction to Logic Circuits & Logic Design with VHDL by Brock J LaMeres
He was my instructor in college and the text itself is extremely helpful for all things FPGA.
I'm sure each person here is talking about a slightly different assignment, course, and book; but for me (from an EE side of the coin) the person that wrote this book taught our 2 semester course series that starts with basic logic, moves into the circuitry, and then into modeling the entire computer architecture in VHDL on a reasonably inexpensive FPGA (the Altera dev boards are about $100-$200).
The book follows that 2 semester series to a tee, and uses the guy's same in course narrative style (minus smacking the whiteboard @ 8 in the morning and us getting yelled at by the french teacher next door). The writer has won multiple teaching awards from IEEE, and is a real gift to the EE community - as you can tell I have 0 complaints.