I have had some back pain trouble in the past, and I've been told that it's because my muscles are not balanced in terms of strength with other muscles of my body (primarily my abs). For a while I was really obsessed with building up a mean looking set of abs, but I neglected to work my lower back. So, I was woundering if anyone had any advice for how to build up my lower back muscles. Does anyone have some good lower back exercises, and if so, how long and often should I perform them.

deadlifts!  do them 2-3 times a week with and i stress this, PERFECT FORM.

yep. whoever told you  about the muscle imbalance is most likely RIGHT ON.   strong tight abs and a weak back = disastrous posture.  and bad posture can lead to back pain.   

it's like half your core is strong, while the other half is really weak.. no doubt you are in pain. 

soccer nailed it.  deads.   and you had better focus real hard on your form.  mess up on your form and go up too fast in weight and your asking for an injury and even MORE back pain.

not trying to scare you.. but never EVER try to impress people at the gym with weights, especially deads.  your spine can handle weight, but only if executed properly.   just start low, and very slowly work your way up as you feel more comfortable.

good morning, GHR, hytper-extensions

thanks guys.
 
I think I'll start with some of the body weight resistance training methods I just learned form a friend instead though. I realize how much of a tightrope walk lower back workouts are, and so that's why I asked a girl at my school, who is training to be a pt. She has books filled with exercises thank god. The 2-3 times a week definatley helps me out though.