Brother Curls all the way!
In my experience I've found that throwing in Brother Curls every second arm workout really shocks the crap outta your bi's.
If you haven't heard of these, they basically work like this:
You and your training partner grab an Ez-Bar and load it with enough weight so that you can both get 10 reps relatively easily. Then you start it off by doing your set of 10 then once finished hand it over immediately to your partner for his set. He does the same then you, then him and so on...
The idea is that you should go until failure, but around 5-7 sets generally fries my biceps.
My arms started really responding when I brought these into my routine.