I picked up Beginning J2ME (http://www.amazon.com/Beginning-J2ME-Novice-Professional-Thi...) earlier this year when working on a mobile application for BB and it was pretty handy. You should know that RIM provides additional apis on top of J2ME that let you create more native-feeling BB applications (and it's worth learning imo) - for this I used tutorials online and RIM's api documentation.
The developer of BBSmart, Neil Sainsbury, used to have a really helpful blog at http://devberry.com, but I believe he took it down after his frustrations with RIM (it's like "shouting at a brick wall").
The developer of BBSmart, Neil Sainsbury, used to have a really helpful blog at http://devberry.com, but I believe he took it down after his frustrations with RIM (it's like "shouting at a brick wall").