I second (or is that third or fourth?) the recommendations for Platemates. 3# is a big jump for biceps and triceps, and also for shoulders. Many weight training books recommend not increasing my more than 5% for upper body and 10% for lower body. Of course, that's not always possible, but you've gotten some good recommendations for working your way up.
Another thing to try would be to make increases in exercises where you are using a barbell, since you can buy 1.25# weight plates, or even get some large washers at the hardware store (weigh them, though, as they are not all the same weight) to micro-load (going up by very small increments that your body doesn't really notice as much). Since the additional weight is divided by two, you would only be going up 1.25# per arm. (1.25# rubber-coated weights are available through fitness1st.com they are in the section with the Troy Lite Barbell set).