For Non-U/S blocks:
Peripheral Nerve Blocks: Principles and Practice by Hadzic.
Great book. Really THE book for your regional month as far as I'm concerned. Only thing it lacks is the Supraclavicular block. Which is the money block. Learn it the old fashioned way "see one, do one, teach one."
For U/S blocks:
Perioperative Diagnostic and Interventional Ultrasound with DVD by Elsevier.
Not the greatest book (could use more anatomy), the DVD makes it worth it. Will give you the basics for the PNB's and has some other crap in it about echo's and access.