Dumbells are great for working out almost any part of your upper body.
You can work out your abs and pecs by doing dumbell presses (if you have a bench). Work out your shoulders, traps, and deltoids by doing shoulder presses. You can work out your triceps by doing tricep extensions, obviously you can do bicep curls.
The workouts are endless with dumbells. Just remember that its important to not take long breaks in between sets otherwise your ruining your workout.
Another great benefit to dumbbells is the fact most workouts that you'll be performing is also working out your core. Kill two birds with one stone