I'm still in the process of grinding my way out of 5NL...but I am
grinding out of it! Here's what's helped me:
* Crushing the Microstakes by BlackRain79
. This book is seriously the "to get" book for the micros. It's authored by the #1 micro player in the world (in terms of volume and winnings)
* Mental Game of Poker (http://www.audible.com/pd/Sports/The-Mental-Game-of-Poker-Audiobook/B0083WSQD0/ref=sr_1_2?qid=1382929900&sr=1-2). My biggest leak was tilting, so this book is helping me out a lot. Check it out on audible and listen to it on your commute.
Actually, on Audible, they have a good collection of books on audio so if you commute a lot you can just get a membership there and get a book or two a month.