For VHDL, although it shouldn't be your only source, the Free Range VHDL book is free and well regarded.
I actually had found this book myself, but only read the first three chapters, it seems to have a bit of a slow start, so i got bored and tossed it. But if you recomend it, i maybe give it a second shot.
Well, it's not ideal and addresses a large audience, but you could "fast forward" and learn a few things though.
I have never stumbled upon *the one* book that sums it all nicely. Your best bet will be a collection of various sources. Which is good, otherwise you may find yourself trapped in the biases of one specific author. And you'll quickly find out that digital designers are ones of the most stubborn people out there.
Another "classic" book is: "The designer's guide to VHDL" - Morgan Kauffman, which I find good but contains occasional outdated stuff.
I also suggest reading the latest VHDL standard (1076-2008) if you can get ahold of it (official versions are expensive). Always good to get your information from the official reference.
Also, I'd suggest learning to use test benches - they are invaluable and pretty much mandatory for verification & validation activities.
So it was no contact issues it was picked up noise, most likely from the nearby clock lead... lesson learned the hard way.
To pick up such high levels of noise means that either you had a contact issue (which you're stating you weren't), or your ground connection was not right (ground loop), which would be typical if you connect your probe's ground to a "remote" ground point (best practice is to connect it to a ground point as close to your signal as you can).
On some occasions, the ground clip's lead of a probe itself can form a loop from which you can get inductively coupled noise from.