Dumbbells are free weights that allow for a more concentrated movement and hence are part of most strength training programs when it comes to building arm strength.
The barbell curl has stood the test of time as a great isolation workout that works both the upper arms and forearms to build strength and stimulate muscle growth in that region.
The close-grip barbell press focuses primarily on the triceps with minimal load on the chest. It is a great exercise for building strength while isolating a muscle group as well.
To isolate and build your trap muscles, dumbbell shrugs are an excellent exercise. You can do these with either a barbell or dumbbell.
The cable rows isolate your back muscles and form a stable engagement for muscle growth in many strength training and weight lifting programs.
The lat pull down is excellent for building upper back, especially your lats in isolation. You can either do this with a wide-grip or underhand grip.