I agree with Judy's recommendations of Gordes, Roussillon, and Lourmarin. Bonnieux is also has outstanding views.
Depending on the day of the week, you could visit the local outdoor market: Lourmarin's market is Friday (highly recommend), Roussillon's is Wednesday, Gordes' and Vaison la Romaine's is Tuesday.
I would definitely try to visit one or two of the hill towns. Enjoy the view, have a leisurely outdoor meal, people watch, stroll around the village enjoying the sights and sounds.
If you are going in the summer, late June or July, you can visit the lavender fields.