I just took the test in April and passed. Here are my suggestions
Sources - The sources I used on the test and to study are:
NEC 208 Code (of course!)
Standard Handbook for Electrical Engineers ( I only used it for a couple things like Lightning protection, Ground testing, explaination on overcurrent protection devices, current limiting, etc.)
Power system Analysis - Bergen and Vittal http://www.amazon.com/Power-Systems-Analysis-Arthur-Bergen/dp/0136919901 (Good for symmetrical components, power flow and any qualitative questions that come up on Generation systems)
EERC - I used an older one which had a lot of useless stuff for the new test. I don't think I used it on the test. The practice question guide has some good practice questions so maybe get that only. http://www.amazon.com/Practice-Problems-Electrical-Engineering-Exam/dp/1591260973
NCEES Practice Problems - http://www.ncees.org/Exams/Study_materials.php?exam=PE&product=1S Buy this book. Its worth it. Flip through it early but don't practice too many of the problems too early or else you'll likely forget them!
My home made reference manual - By far the most useful on the test. This was the product of my studying.
Go here http://www.ncees.org/Exams/PE_exam.php, click on the electrical power test and download the PDF. This has all the sections of things that may be on the test. Begin to make your own reference manual in a 3 ring binder with a section for each topic listed. Have a note sheet of photocopy for each section. Any practice problems related to sections, I would rewrite myself, catalog them so I could find them later, and organized into the manual.
A few hints on sections
Engineering Econ: Just get the notes out of the FE manual.
Per Units: know how to change bases. Good link http://www.cadickcorp.com/papers.htm. The Bergen book is good too.
Batteries: Any book on photovoltaics will likely have a good section on batteries.
Relaying Schemes: Look up Relay #s
Get out your old circuits and electronics books and relearn that stuff. buy Schaum's solved problems for electric circuits. Don't make the mistake I did and study only exam prep books. I failed when I studied to pass the test but passed when I relearned the stuff. Good luck